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GUIDE 


STUDY  OF  COMMON  PLANTS 


AN  INTRODUCTION  TO  BOTANY 


BY 


VOLNEY   M.   SPALDING 

PROFESSOR  OF  BOTANY  IN  THE  tTNivERSiTY  OF  MICHIGAN 


BOSTON,   U.S.A. 
D.    C.   HEATH   &   CO.,   PUBLISHEES 

1894 


K 


COPYRIGHT,  1893, 
BY  VOLNEY   M.   SPALDING. 


Typography  by  J.  S.  Gushing  &  Co. 
Presswork  by  S.  J.  Parkhill  &  Co, 


PREFACE. 


THESE  exercises  have  been  prepared  for  classes  in  high 
schools  and  other  institutions  of  similar  grade,  and  are 
intended  to  indicate,  in  a  general  way,  the  nature  of  the 
work  that  in  the  judgment  of  the  writer  should  be  under- 
taken with  young  people  who  are  just  beginning  the  sys- 
tematic study  of  common  forms  of  plant  life.  They  were 
suggested  by  frequent  inquiries  of  teachers  regarding  the 
preparation  in  botany  now  required  for  admission  to  the 
University  of  Michigan. 

No  originality  is  claimed  for  the  subject-matter  or  its 
treatment,  although  much  time  has  been  spent  in  the 
effort  to  develop  a  natural  and  practicable  method  of 
approaching  the  study  of  living  things.  While  the  study 
of  relationship  holds  the  first  place,  the  attention  of  the 
pupil  is  directed  at  every  step  to  the  physiological  signifi- 
cance of  observed  facts ;  and  although  this  will  hardly  be 
approved  by  those  who  attempt  to  separate  sharply  the 
domain  of  morphology  from  that  of  physiology,  it  has 
seemed  to  the  writer  better  to  follow  Nature  than  be 
cramped  by  such  artificial  barriers.  Some  of  the  exer- 
cises will  perhaps  appear  too  simple  -and  others  too  diffi- 
cult, but  a  judicious  selection  on  the  part  of  the  teacher 
will  do  much  to  correct  this. 

As  to  the  ground  that  ought  to  be  covered  in  such  a 
course,  and  the  proper  sequence  of  subjects,  there  is  natu- 


iy  PREFACE. 

rally  great  difference  of  opinion  among  practical  teachers. 
Theoretically  it  would  seem  best  to  begin  with  the  lowest 
forms  of  plants,  and  work  up  to  the  higher;  but  after 
careful  consideration,  and  in  view  of  the  actual  state  of 
things  in  most  of  our  preparatory  schools,  a  different  plan 
has  been  adopted. 

It  is  hoped  that  in  spite  of  mistakes  and  imperfections, 
sure  to  be  brought  to  light  if  the  book  is  used,  it  may  never- 
theless prove  serviceable  to  a  rapidly  increasing  number 
of  teachers  who  are  desirous  of  improving  existing  methods 
of  instruction.  To  Dr.  Erwin  F.  Smith  of  Washington, 
D.C.,  and  Miss  Effie  A.  Southworth  of  Barnard  College, 
who  have  kindly  read  the  proofs  throughout ;  to  Mr. 
W.  H.  Rush  of  the  University  of  Michigan,  who  has  criti- 
cally reviewed  and  tested  the  practical  directions;  and 
to  others  who  have  aided  in  various  ways,  the  sincere 
thanks  of  the  writer  are  due. 


CONTENTS. 


PAgE 

To  THE  STUDENT     ..........  ix 

To  THE  TEACHER     ..........  xii 

WORKS  OF  REFERENCE    .........  xv 

LABORATORY  AND  PERMANENT  OUTFIT    ......  xix 

ORGANS  OF   FLOWERING   PLANTS. 

I.     SEEDS   ...........  1 

II.     GROWTH  OF  PLANTS  FROM  THE  SEED.         ....  20 

III.  ROOT 29 

IV.  STEM 38 

V.     LEAF 57 

VI.     FLOWER 74 

VII.     FRUITS 88 

NATURAL   GROUPS   OF   PLANTS.1 

VIII.     ALG^E         .         .         .         .         .         .         .         .         .         .  96 

IX.     MUSCINE^E 105 

X.     FILICINE^E 114 

XI.     EQUISETINE^E 123 

XII.     LYCOPODINE^E 127 

1  Groups  above  families  have  been  placed  in  boldface  type  without  attempting  their 
coordination. 


CONTENTS. 


GYMNOSPERMS. 

PAGE 

XIII.     CONIFERS    .  132 


MONOCOTYLEDONS. 

XIV.     GRAMINE^E .         .         .137 

XV.  CYPERACE^E.        ........  141 

•        XVI.     ARACE.E 144 

XVII.     LILIACE^E     .         . 148 

XVIII.  AMARYLLIDACE.E           .......  150 

XIX.     IRIDACE*: 152 

XX.  ORCHIDACE^E        ........  155 

DICOTYLEDONS. 

XXI.     SALICACE^E 161 

XXII.     RANUNCULACE^E 164 

XXIII.  CRUCIFER.E 171 

XXIV.  ROSACES 174 

XXV.  LEGUMINOS^E          ........  177 

XXVI.     GERANIACE^E 181 

XXVII.     EUPHORBIACE^: 186 

XXVIII.     ACERACE^ 190 

XXIX.     MALVACE.E 193 

XXX.     VIOLACE*: ...  196 

XXXI.     ONAGRACE^E 200 

XXXII.     UMBELLIFER.E 203 

XXXIII.  ASCLEPIADACE^E    ...  ....  208 

XXXIV.  BORRAGINACE^: 212 

XXXV.  LABIATE  215 


CONTENTS.  Vll 

PAGE 

XXXVI.       SOLANACE^ 219 

XXXVII.       SCROPHULARIACE^E           .             .            .       ^   .            .            .             .  223 

XXXVIII.     CAPRIFOLIACE*:    ........  228 

XXXIX.       CUCURBITACE^E 231 

XL.     COMPOSITE  .  235 


TO   THE   STUDENT. 


You  are  beginning  the*  study  of  living  things,  and  it  is 
very  important  that  you  should  begin  in  the  right  way. 
These  practical  exercises  are  intended  to  help  you,  but  not 
to  do  the  work  for  you.  Many  of  the  exercises  will  seem 
very  simple,  but  if  you  actually  do  what  is  called  for,  it 
will  be  plain  why  so  much  stress  is  laid  on  knowledge 
gained  by  direct  personal  observation  and  experiment.1 

There  are  a  few  things  that  you  ought  to  consider  at  the 
outset. 

1.  First  of  all,  it  is  essential  that  you  should  learn  to 
see  things  just  as  they  are,  and  to  report  exactly  what 
you  have  seen.  Agassiz  used  to  say  to  his  students: 
"Study  to  know  what  is;  be  courageous  enough  to  say 
4 1  do  not  know.'  "  Tyndall  said  to  the  teachers  at  South 
Kensington :  "  In  every  one  of  your  experiments  endeavor 
to  feel  the  responsibility  of  a  moral  agent.  ...  If  you 
wish  to  become  acquainted  with  the  truth  of  Nature,  you 
must  from  the  first  resolve  to  deal  with  her  sincerely." 
Darwin  in  his  autobiography2  writes:  "  I  had  during  many 

1  "  You  wish,  for  example,  to  get  a  knowledge  of  magnetism  ;  well,  pro- 
vide yourself  with  a  good  book  on  the  subject,  if  you  can,  but  do  not  be 
content  with  what  the  book  tells  you  ;    do  not  be  satisfied  with  its 
descriptive  woodcuts ;  see  the  actual  thing  yourself.     Half  of  our  book- 
writers  describe  experiments  which  they  never  made."  — TYNDALL,  Frag- 
ments of  Science. 

2  Life  and  Letters,  p.  71. 

ix 


X  TO   THE   STUDENT. 

years  followed  a  golden  rule,  namely,  that  whenever  a 
published  fact,  a  new  observation  or  thought,  came  across 
me,  which  was  opposed  to  my  general  results,  to  make  a 
memorandum  of  it  without  fail  and  at  once,  for  I  had 
found  by  experience  that  such  facts  and  thoughts  were  far 
more  apt  to  escape  from  the  memory  than  favorable  ones." 

2.  When  you  have  seen  a  thing  clearly,  be  sure  to  express 
your  conception,  whether  by  drawing,  or  written  descrip- 
tion, or  both,  as   accurately  as   possible.     Learn  to  use 
scientific  language  with  precision.     Write  out  your  obser- 
vations  in  full,  in  the  best  English  at   your  command. 
Avoid   abbreviations  and   every  other  device  for  saving 
time.     Make   your   drawings  so   that  an  engraver  could 
copy  them.     Do  not  hesitate  to  do   your  work  all  over 
again,  if  it  can  be  improved,  as  it  probably  can  be,  and  do 
not  leave  a  thing  until  you  have  not  only  a  complete  obser- 
vation, but  a  complete  expression  of  it. 

3.  Do  not  be  hasty  in  drawing  conclusions.     Make  a 
constant  practice  of  comparing  the  object  you  are  studying 
with  others  of  the  same  kind.     Note  differences  and  resem- 
blances.    Learn  by  the  actual  process  what  it  is  to  acquire 
a  general  conception.     "  Honesty  in  science  means,  first, 
facts  well  proved,  and  then  conclusions  slowly  and  pain- 
fully  deduced   from   facts   well    proved."1     In   all    your 
work  stop  and  think.     The   mere  accumulation  of  facts, 
if  nothing  is  done   with  them,   is  of  little  consequence. 
Constantly  ask  the  question,  what  does  this  fact  mean  ? 
You  may  or  may  not  be  able  to  answer  the  question,  but 
that  is  no  reason  for  not  raising  it. 

4.  Cultivate  self-reliance,  but  not  self-sufficiency.     Study 

1  J.  P.  Lesley,  Presidential  Address,  Am.  Assn.  for  the  Advancement 
of  Science,  1885. 


TO   THE   STUDENT.  XI 

things  themselves  rather  than  book  descriptions  of  them, 
but  habitually  use  the  books  you  are  referred  to,  compar- 
ing point  by  point  your  own  observations  with  what  the 
authors  have  to  say.  The  writers  cited  may  or  may  not 
be  right ;  they  are  more  likely  to  be  than  you  are ;  but 
both  of  you  may  be  wrong.  The  best  way  is  to  observe  for 
yourself,  then  consult  the  books ;  then  observe  again,  and 
continue  your  observations  and  comparisons  until  the  exact 
truth  is  ascertained.  This  is  the  way  investigations  are 
conducted,  and  you  are  learning  how  to  investigate. 

5.  This  leads  to  a  word  on  the  use  of  books.  Make  it 
a  regular  practice  to  look  up  the  references  that  are  given 
with  the  exercises.  By  doing  this  you  will  not  only 
become  acquainted  with  some  of  the  most  valuable  botan- 
ical literature,  but,  what  is  more  important,  you  will  come, 
in  some  measure,  to  understand  the  habits  and  methods  of 
the  great  workers  in  science,  and  will,  perhaps  insensibly  to 
yourself,  catch  something  of  their  spirit,  and  learn  to 
work  as  they  did,  honestly,  accurately,  and  "  with  infinite 
patience." 

One  of  the  greatest  investigators  who  has  ever  lived 
wrote  a  few  years  ago :  "  Whenever  I  have  found  out  that 
I  have  blundered,  or  that  my  work  has  been  imperfect, 
and  when  I  have  been  contemptuously  criticised,  and  even 
when  I  have  been  over-praised,  so  that  I  have  felt  morti- 
fied, it  has  been  my  greatest  comfort  to  say  hundreds  of 
times  to  myself  that  '  I  have  worked  as  hard  and  as  well 
as  I  could,  and  no  man  can  do  more  than  this.' " 1 

1  Charles  Darwin,  Life  and  Letters,  p.  72. 


TO    THE   TEACHER. 


MATERIAL  AND   METHODS. 

IN  order  to  use  these  exercises  successfully  it  will  be 
necessary  to  adopt  the  laboratory,  as  distinguished  from 
the  text-book,  method  of  instruction.  The  practice,  still 
too  common,  of  using  ordinary  recitation  seats  and  benches 
for  work  of  this  kind  is  extremely  unsatisfactory,  and 
ought  to  be  abandoned.  The  best  arrangement  is  to  have 
places  assigned  at  long  tables  —  one  table  in  front  of  each 
window,  so  that  every  student  can  have  a  full  amount  of 
light.  North,  east,  and  west  windows  are  preferable,  those 
on  the  north  side  being  the  best.  In  every  case  the  pupil 
is  to  be  provided  with  the  material  called  for,  and  this 
should  be  typical  of  its  kind  and  sufficient  in  quantity. 
In  a  large  proportion  of  the  exercises  the  plants  needed 
are  common  everywhere  and  easily  obtained.  When  it  is 
impossible  to  procure  them  the  exercise  is  to  be  omitted. 
It  has  no  significance  whatever  unless  the  thing  talked 
about  is  actually  present  to  the  eye.  It  will  generally  be 
found  better  to  secure  an  appropriation  of  a  few  dollars 
and  employ  some  one  regularly  to  furnish  a  supply  of 
material  than  to  depend  on  what  the  teacher  and  members 
of  the  class  can  gather.  In  any  case  the  things  to  be 
studied  must  be  systematically  provided.  They  cost  far 
less,  but  are  just  as  essential  as  the  reagents  and  apparatus 
in  a  chemical  or  physical  laboratory. 


TO   THE   TEACHER.  Xlll 

Too  much  emphasis  cannot  be  laid  on  the  importance 
of  securing  at  the  outset  a  fairly  complete  equipment. 
The  necessity  of  following  the  laboratory  method  in  science 
teaching  is  now  so  universally  recognized  that  it  is  to  be 
hoped  that  boards  of  education  will  generally  adopt  the 
better  way  and  cheerfully  pay  for  it.  Having  once  secured 
the  necessary  tables,  instruments,  and  books,  the  expense 
from  year  to  year  is  extremely  small  in  comparison  with 
the  result  aimed  at,  viz.  a  discipline  that  can  be  attained  in 
no  other  ivay. 

The  use  of  the  microscope,  methods  of  sectioning, 
mounting  microscopic  objects,  drawing,  and  other  prac- 
tical operations  of  the  laboratory  are  best  learned  of  the 
living  teacher.  Useful  suggestions,  however,  will  be  found 
in  the  excellent  handbooks  of  Strasburger,  Arthur,  Barnes, 
and  Coulter,  and  other  laboratory  manuals. 

DISPOSITION   OF   TIME. 

When  practicable,  it  is  much  more  advantageous  to 
arrange  the  time  given  to  laboratory  work  so  that  each 
student  can  work  two  consecutive  hours  for  a  certain  num- 
ber of  days  each  week.  When  this  cannot  be  done  with- 
out seriously  interfering  with  the  school  programme,  the 
following  plan  is  suggested:  Give  four  hours  each  week 
to  practical  exercises,  requiring  each  member  of  the  class 
to  work  independently  in  his  own  place,  precisely  as  he 
would  at  a  table  in  a  chemical  laboratory,  the  teacher  pass- 
ing from  table  to  table,  giving  personal  help  as  it  is  needed, 
and  from  time  to  time  giving  notes  and  directions  to  the 
class  as  a  whole.  The  remaining  hour,  say  on  Friday  or 
Monday,  or  sometimes  both,  may  be  used  for  recitations, 
reports  on  laboratory  work,  and  the  dictation  of  notes  and 


TO   THE   TEACHER. 

references.  Exercises  to  be  conducted  out  of  school  hours 
may  be  assigned  at  the  discretion  of  the  teacher,  but 
generally  it  will  be  found  that  the  best  work  is  done  in 
the  laboratory  under  his  personal  direction. 

In  the  majority  of  preparatory  schools  half  a  year  is 
given  to  botany.  It  is  very  desirable  that  the  time  should 
be  extended,  but  until  this  is  done  it  is  recommended 
that  the  exercises  be  followed  substantially  as  here  out- 
lined, with  the  omission  of  a  part,  or  possibly  the  whole,  of 
the  microscopic  work.  If  the  latter  is  undertaken,  and  a 
reasonable  amount  of  time  is  given  to  the  study  of  different 
families  of  plants  in  the  spring,  a  full  year  will  be  needed. 


WORKS    OF   REFERENCE. 


IN  connection  with  the  exercises,  frequent  references 
are  given.  In  a  few  cases  books  of  a  more  or  less  popular 
character  are  mentioned,  and  some  of  the  most  important 
works  in  French  and  German  are  referred  to,  inasmuch 
as  they  are  well-nigh  indispensable  to  the  teacher.  In 
general,  the  works  named  are  easily  obtained,  and  ought  to 
have  a  place  in  any  respectable  school  library.  Several 
copies  of  the  books  in  constant  use  should  be  placed  on 
tables  in  the  laboratory,  where  they  can  be  consulted  with- 
out loss  of  time,  the  students  being  given  to  understand 
that  they  are  expected  to  look  up  references  as  habitually 
and  critically  as  they  would-  if  reading  a  classical  author. 
One  or  more  of  the  best  periodicals  may  properly  be 
included  in  the  essentials  of  the  laboratory  outfit.  The 
following  list,  by  no  means  complete,  includes  some  of  the 
most  generally  useful  botanical  works. 

LABORATORY   MANUALS. 

Arthur,  Barnes,  and  Coulter,  Plant  Dissection.    Henry  Holt  &  Co.,  New 

York,  1886. 
Bower  and  Vines,  Practical  Botany,  Parts  I.  and  II.    Macmillan  &  Co., 

London,  1885  and  1887. 

Clark,  Practical  Methods  in  Microscopy.  D.  C.  Heath  &  Co.,  Boston,  1893. 
Strasburger  and  Hillhouse,  Practical  Botany.    Macmillan  &  Co.,  New 

York.     1889. 

These  manuals  are  of  the  utmost  value  as  laboratory  guides. 

The  first  is  the  simplest,  and,  on  the  whole,  most  suitable  for 


Xvi  WORKS    OF   REFERENCE. 

beginners.  The  third  contains  the  latest  and  most  approved 
methods  of  microscopical  manipulation.  The  last  is  most  com- 
plete, and  gives  the  modern  methods  of  work  jvith  such  clearness 
and  detail  as  to  render  it  indispensable  in  every  botanical  labo- 
ratory. The  original  work  of  which  it  is  a  translation  [Stras- 
burger,  Das  kleine  botanische  Praktikum.  Fischer,  Jena]  will  be 
preferred  by  those  who  read  German. 

STRUCTURAL   AND   PHYSIOLOGICAL. 

Gray,  Structural  Botany  (sixth  edition).  Ivison,  Blakeman  &  Co.,  New 
York,  1879. 

Goodale,  Physiological  Botany.  Ivison,  Blakeman  &  Co.,  New  York, 
1885. 

Bessey,  Botany.     Henry  Holt  &  Co.,  New  York,  1888. 

DeBary,  Comparative  Anatomy  of  the  Phanerogams  and  Ferns.  Oxford, 
Clarendon  Press,  1884. 

Vines,  Physiology  of  Plants.     Cambridge,  University  Press,  1886. 

Sachs,  The  Physiology  of  Plants,  Trans,  by  H.  Marshall  Ward.  Oxford, 
Clarendon  Press.  Macmillan  &  Co.,  1887. 

Haberlandt,  Physiologische  PJlanzenanatomie.  Engelmann,  Leipzig, 
1884. 

Frank,  Lehrbuch  der  Pflanzenphysioloyie.     Parey,  Berlin,  1890. 

Zimmermann,  Die  Morphologic  und  Physiologie  der  Pflanzenzelle . 
Trewendt,  Breslau,  1887. 

Detmer,  Das  pjlanzenphysiologische  Praktikum.     Fischer,  Jena,  1888. 

Detmer,  Manuel  technique  de  Physiologie  vegetale.  C.  Reinwald,  Paris, 
1890.  Translation  of  the  last-named  work  revised  and  extended 
by  the  author. 

Bessey 's  Botany  is  the  least  expensive  book  that  covers  the 
ground  at  all  satisfactorily.  With  Gray's  Structural  and  Good- 
ale's  Physiological  Botany  one  is  better  equipped  for  work,  inas- 
much as  the  whole  general  subject  of  organography  and  physiology 
is  ably  and  clearly  presented  in  them.  Sachs'  Lectures  on  the 
Physiology  of  Plants  is  indispensable. 

MORPHOLOGICAL   AND   SYSTEMATIC. 

Goebel,  Outlines  of  Classification  and  Special  Morphology  of  Plants. 

Oxford,  Clarendon  Press,  1887. 
Luerssen,  Handbuch  der  Systematischen  Botanik.    Haessel,  Leipzig,  1879. 


WORKS    OF   REFERENCE.  XVII 

Eichler,  Bluthendiagramme.     Engelmann,  Leipzig,  1875. 

Engler  und  Frantl,  Die   naturlichen   Pflanzenfamilien.      Engelmann, 

Leipzig. 

All  of  these  are  of  great  value,  especially  the  rather  expensive 

work  of  Engler  and  Prantl,  now  in  course  of  publication. 

FLORAS. 

Gray,  Manual  of  Botany  (sixth  edition).     Ivison,  Blakeman  &  Co., 
New  York. 

Chapman,  Flora  of  the  Southern  United  States  (second  edition).     Ivi- 
son, Blakeman  &  Co.,  1883. 

Coulter,  Manual  of  the  Botany  of  the  Rocky  Mountain  Region.     Ivison, 
Blakeman  &  Co.,  1885. 

Coulter,  Manual   of  the   Phanerogams   and   Pteridophytes   of   Western 
Texas.     U.  S.  Dept.  Agric.,  1892. 

Gray,  Synoptical  Flora  of  North  America.     (In  progress.) 

Gray's  Manual  is  commonly  bound  with  the  "  Lessons  "  in  one 
volume,  but  may  be  had  separate  in  convenient  form  for  the 
pocket.  Dr.  Gray's  final  revision  of  the  "Lessons"  has  been  pub- 
lished under  the  title,  Elements  of  Botany.  Ivison,  Blakeman  & 
Co.,  1887. 

CRYPTOGAMIC   BOTANY. 

Eaton,  Ferns  of  North  America.     Cassino,  Boston,  1879. 

Lesquereux  and  James,  Mosses  of  North  America.     Cassino,  Boston, 

1884. 
Farlow,  Marine   Algce   of  New   England.     U.   S.    Fish    Commission, 

Washington,  1881. 

Tuckerman,  North  American  Lichens.     Cassino,  Boston,  1882. 
DeBary,  Comparative  Morphology  and  Biology  of  the  Fungi,  Mycetozoa, 

and  Bacteria.     Oxford,  Clarendon  Press,  1887. 

v.  Tavel,  Vergleichende  Morphologie  der  Pilze.     Fischer,  Jena,  1892. 
Bennett  and  Murray,  Handbook  of  Cryptogamic  Botany.     Longmans, 

Green  &  Co.,  London  and  New  York,  1889. 
Plowright,  British  Uredinece  and  Ustilaginece.     Kegan  Paul,  Trench  & 

Co.,  London,  1889. 
Underwood,   Our  Native   Ferns   and   their   Allies.     Bloomington,  111., 

1882. 


XV111  WORKS    OF   REFERENCE. 

The  list  of  works  on  Cryptogamic  Botany  might  be  greatly 
extended.  Numerous  references  to  the  literature  of  the  algae 
will  be  found  in  Farlow's  work  mentioned  above,  and  to  that  of 
the  fungi  in  DeBary's  treatise.  For  other  references  consult  Ben- 
nett and  Murray's  Handbook. 

GENERAL. 

Miiller,  The  Fertilization  of  Flowers.     Macmillan  &  Co.,  London,  1883. 
DeCandolle,  Origin  of  Cultivated  Plants.     Appleton  &  Co.,  New  York, 

1885. 

Kerner,  Flowers  and  their  Unbidden  Guests.     Paul  &  Co.,  London,  1878. 
Darwin,  Insectivorous  Plants,  and  other  works.     Appleton  &  Co.,  New 

York. 

Lubbock,  Seedlings.     Appleton  &  Co.,  New  York,  1892. 
Lubbock,  Flowers,  Fruits,  and  Leaves.     Macmillan  &  Co.,  London, 

1886. 

Goodale,  Wild  Flowers  of  America.     Cassino,  Boston,  1882. 
Sachs,  History  of  Botany.     Macmillan  &  Co.,  1890. 
Lindley  and   Moore,  The    Treasury  of  Botany.     Longmans,  London, 

1874. 
Kerner  von  Marilaun,  Pflanzenleben,  2  vols.     Bibliographisches  Insti- 

tut,  Leipzig  and  Vienna,  1891. 

M tiller's  work  on  the  Fertilization  of  Flowers  gives   references 

to  the  immense  and  increasing  body  of  literature  on  this  subject. 

Kerner's  work  is  out  of  print,  but  may  occasionally  be  picked  up, 

and  is  a  most   charming    little  book.     All   of   Darwin's   books 

should  have  a  place  in  such  a  list. 

CURRENT   LITERATURE. 

The  Botanical  Gazette.     Lake  Forest,  111.,  $2.50  per  year. 

Bulletin  of  the  Torrey  Botanical  Club.     New  York,  $2.00  per  year. 

Annals  of  Botany.     Oxford,  Clarendon  Press. 

Botanisches  Centralblatt.     Gotthelft,  Cassel. 

The  Botanical  Gazette  and  Torrey  Bulletin  are  well-known  Ameri- 
can journals.  The  Annals  of  Botany  is  a  new  periodical  of  a 
high  order,  with  original  monographs,  criticisms  of  current  lit- 
erature, etc.  The  Botanisches  Centralblatt  is  indispensable  in 
botanical  research. 


LABORATORY  AND  PERMANENT  OUTFIT. 


1.  The  laboratory   should   be  a  large   room,  properly 
ventilated,  with  as  many  windows  as  practicable,  and  used 
exclusively  as  a  laboratory.     An  upper  room  is  preferable 
to  a  lower  one,  since  the  air  is  clearer  and  there  is  less 
liability  to  disturbance  from  passers-by. 

2.  The  laboratory  tables  should   be  plain  and  solid, 
oiled,  but  not  painted  or  varnished,  and  large  enough  to 
give  each  student  all  the  space  he  requires  without  crowd- 
ing.    Drawers  should   be  placed   in  the    tables,   or   in  a 
separate  case,  in  which  the  students'  outfit  may  be  kept. 

3.  Receptacles     for    waste     materials,    conveniently 
placed    and    frequently    emptied,    and    plenty    of    clean 
water  are  indispensable. 

4.  A  pair  of  balances,  such  as  are  employed  by  drug- 
gists for  accurate  weighing,  will  be  required. 

5.  Microscopes.      For  the   compound   microscope,  the 
so-called  continental  stand  is  preferable,  on  account  of  its 
simplicity,  firmness,  and  convenient  size.     Two  good  objec- 
tives, I  and  J  inch,  or  their  equivalent,  and  two  eye-pieces 
are  necessary.     Such  an  instrument  may  be  purchased  of 
a  reliable  dealer  for  about  §30.     It  will  hardly  be  practi- 
cable to  equip  the  laboratory  with  lower-priced  ones  that 
will  prove  satisfactory. 

Dissecting  microscopes  of  simple  construction  are  needed, 


XX       LABORATORY  AND  PERMANENT  OUTFIT. 

but  a  good  hand-lens,  properly  mounted,  will  answer  the 
same  purpose.  See  Arthur,  Barnes,  and  Coulter,  Plant 
Dissection,  p.  2. 

6.  Glassware  and  miscellaneous  articles.     A  stock  of 
common  plates  and  bowls,  beakers,  glass  tubing,  bell-jars, 
test-tubes,  metric  rules,  etc.,  will  be  required,  but  are  best 
purchased  as  needed,  at  the  discretion  of  the  teacher. 

REAGENTS. 

Of  the  reagents  most  employed  in  botanical  work  the 
following  are  required : 1  - 

7.  Alcohol.      For   preserving   plant-tissues,   except   in 
cases  involving  the  most  delicate  operations,  three  grades 
of  alcohol  are  all  that  will  be  needed.     The  lowest  grade 
(between  45  and  §0  per  cent)  is  composed  of  equal  parts 
of  alcohol  of  commerce  and  distilled  water.      The  inter- 
mediate grade  (between  70  and  75  per  cent)  is  prepared 
by   adding    25    parts   of   distilled    water   to    75   parts   of 
commercial  alcohol.     The  highest  grade  is  the  alcohol  of 
commerce  (approximately  95  per  cent). 

Parts  of  plants  to  be  preserved  are  allowed  to  remain 
24  hours  in  the  lowest  grade  of  alcohol,  then  for  the  same 
length  of  time  in  alcohol  of  intermediate  strength,  and 
finally  are  placed  in  95  per  cent  alcohol,  in  which  they 
may  be  kept  indefinitely.  It  is  necessary  to  guard  against 
attempting  to  preserve  too  much  material  in  a  given 
quantity  of  alcohol,  as  decomposition  is  likely  to  take 
place. 

1  Reference  may  be  made  to  various  works  in  which  reagents  and 
methods  are  discussed  at  much  greater  length.  Among  these  are  Stras- 
burger  and  Hillhouse,  Practical  Botany ;  Behrens,  Guide  to  the  Use  of 
the  Microscope  in  Botany  ;  Zimmermann,  Die  botanische  Mikrotechnik. 


LABORATORY   AND   PERMANENT    OUTFIT.  XXI 

8.  Absolute  alcohol.     For  finer  histological  work  abso- 
lute alcohol  and  a  larger  number  of  grades  of  commercial 
alcohol  more  carefully  prepared  are  necessary. 

9.  Iodine    solution.     Distilled  water    10  c.c.,  potassic 
iodide  1  gm.,  iodine  0.25  gm.     Dilute  to  250  c.c. 

10.  Glycerine.     Pure   glycerine  is   employed   in   some 
cases,  but  equal  parts  of  glycerine  and  distilled  water  will 
generally  be  found  most  serviceable. 

11.  Scnulze's  solution.     This  may  be  prepared  accord- 
ing to  the  rule  given  in  Strasburger's  Praktikum,  but  it 
will  be  found  more  convenient  to  employ  Griibler's  chlor- 
iodide    of    zinc,  which   may  be    obtained   of   Eimer   and 
Amend,  New  York. 

12.  Potash  solution.     One  part  of  solid  caustic  potash 
dissolved  in   20    parts   of   distilled  water.     This   reagent 
attacks   glass,   and  care  should   be   taken  to  prevent  its 
getting  on  the  objectives. 

13.  Glacial  acetic  acid. 

14.  Sulphuric  acid. 

15.  Hydrochloric  acid. 

16.  Picric  acid. 

17.  Phlorog-lucin.     One  per  cent  alcoholic   or  watery 
solution.      Employed    with    hydrochloric   acid   as   a   test 
for  lignin. 

18.  Picric  aniline  blue.     Add  picric  acid  to  distilled 
water  until  a  saturated  solution  is  obtained.     To  this  add 
slowly  a  saturated  watery  solution  of  aniline  blue  until  it 
is  of  a  deep  blue-grSen  color. 


XXli  LABORATORY   AND   PERMANENT   OUTFIT. 

19.  Acetic   methyl   green.     To  a  2  per  cent  solution 
of  glacial  acetic  acid  add  methyl  green  until  the  solution 
is  deeply  colored. 

STUDENT'S    OUTFIT. 

Each  pupil  should  be  provided  with  the  following 
articles : 1  — 

20.  A  Coddington  lens  or  achromatic  triplet.     Either 
of  these  will  serve  a  good  purpose.     The   cheap  lenses, 
mounted   in   horn,  and  sold   for  a  dollar  or  less,  are  of 
little   use.     A  good  Coddington  lens  may  be  purchased 
of  Bausch  and  Lomb,  Rochester,  N.Y.,  for  $2.50,  and  an 
excellent  achromatic  triplet  of  James  W.  Queen  &  Co., 
Philadelphia,  for  14.75. 

21.  A  good  pocket  knife,  kept  sharp. 

22.  Razor   of   good   quality  and  medium  size,  hollow 
ground.     The  Torrey  razor,  manufactured  at  Worcester, 
Mass.,  is  recommended. 

23.  A  pair  of  fine  forceps. 

24.  Slides  and  thin  glass  covers  for  mounting  micro- 
scopic  objects.     The  glass  covers  should  be  of   medium 
thickness,  and  not  less  than  f  of  an  inch  in  diameter. 

25.  Needles  mounted  in  handles. 

26.  Camel's-hair  brushes  of  medium  size. 

27.  Note-book  and  drawing  paper.     The  latter  should 
be  unruled,  rather  heavy,  of  good  quality,  and  cut  to  a 
convenient  size  for  drawings. 

1  In  some  cases  it  may  be  practicable,  in  order  to  save  expense,  for  two 
to  use  the  same  outfit ;  but  the  practice  is  not  to  be  commended,  except 
in  case  of  necessity. 


LABORATORY   AND  PERMANENT   OUTFIT.  XX111 

28.  Drawing-  pencils  and  eraser.  The  pencils  should 
be  of  at  least  two  grades,  medium  and  hard. 

If  the  student  pays  a  laboratory  fee,  most  of  the 
articles  named  above  should  be  furnished  by  the  school 
board ;  if  no  fee  is  charged,  he  may  reasonably  be  required 
to  purchase  for  himself  those  that  are  liable  to  loss  or 
deterioration  through  use. 


STUDY   OF   COMMON   PLANTS. 

I.   SEEDS.1 

MATERIAL    REQUIRED. 

Common  white  beans.     Other  varieties,  such  as  "  butter  beans,"  etc. 

Peas,  oats,  wheat,  Indian  corn,  —  several  varieties  of  the  latter. 

Castor  oil  seeds. 

Seeds  of  white  pine,  Norway  spruce,  and  other  conifers. 

Commercial  "  nuts,"  such  as  chestnut,  peanut,  filbert,  almond,  Brazil 

nut,  and  English  walnut. 
Seeds  of  coffee,  date,  flax,  sunflower,  tomato. 
As  many  kinds  as  possible  of  seeds*with  winged  or  hooked  appendages 

or  other  special  arrangements  for  dissemination. 
Seeds  of  squash,  pumpkin,  watermelon,  muskmelon,  cucumber,  gourd, 

and  similar  collections  from  other  important  families. 

COMMON   BEAN.     Phaseolus  vulgaris,  Savi. 

I.    Compare  a  number  of  white  beans,  and  see  if  they  are 
all  alike.     Select  a  good  specimen.     Observe  and  describe 

1.  The  shape,  surface,  and  color. 

2.  Surface  markings : 

a.    The  scar,  hilum,2  marking  the  place  where  the 
seed  was  attached. 

1  General  references:    Gray,  Structural .  Botany ,  pp.  305-314;   Stras- 
burger,  Practical  Botany,  Chaps.  I  and  II ;  Sachs,  Physiology  of  Plants; 
Haberlandt,  Physiologische  Pfl,anzenanatomie,  pp.  277-293. 

2  If  any  of  the  terms  are  unfamiliar  and  are  not  sufficiently  explained 
in  the  text,  consult  Webster's  International  Dictionary. 

1 


2.  V  :  ;  ;          STUDY  OF  COMMON  PLANTS. 


'i  2>^  Near  the  hilum  a  minute  orifice,  micropyle,  easily 

seen  under  a  lens. 

c.  The  chalaza,  the  part  where  the  seed  coats  blend 
with  each  other  and  nutriment  enters  the  grow- 
ing seed.  In  this  case  the  chalaza  is  located 
externally  by  a  small  protuberance  near  the 
hilum,  on  the  opposite  side  from  the  micropyle. 

II.  With  a  sharp  penknife  or  needle  remove  the  integ- 
ument, testa,  from  a  bean  that  has  been  soaked  in  water 
for   a   day.     Near  the  hilum    a  small  pointed  body,  the 
radicle,  will  be   found.     Locate   it   accurately.      Does   it 
have  any  relation  to  the  micropyle  ? 

III.  Separate    the    two    halves,   cotyledons.      Examine 
under  a  good  lens.     Notice 

1.  The  form  and  position  of  the  radicle. 

2.  The  delicate  structure,  plumule,  connected  with  it. 
Draw  the  parts,  taking  care  to  represent  accurately 

the  leaves  of  the  plumule  and  their  venation. 

IV.  Examine  beans  that  have  lain  a  few  days  on'  moist 
blotting  paper  under  a  bell-jar.     What  changes  have  taken 
place  ? 

What  part  of  the  seed  has  developed  into  the  primary 
root  ?     What  changes  has  the  plumule  undergone  ? 

V.  With  the  common  bean  compare  a  number  of  other 
varieties,   "butter   bean,"   "scarlet   runner,"   etc.,   noting 
carefully  all  points  of  likeness  and  difference. 

VI.  Study  next  the  -common  pea,  comparing  its  struc- 
ture with  that  of  the  bean. 

VII.  Write  a  detailed  account  of  your  observations  of 
the  bean  and  pea.    Introduce  drawings  or  outline  sketches 


SEEDS.  3 

whenever  the  description  will  be  rendered  more  intelligible 
by  them. 

CASTOR  OIL  SEED.     Ricinus  communis,  L. 

I.    Study  first  the  external  features. 

1.  Shape  and  surface.     Compare  different  specimens  as 

regards  shades  and  distribution  of  color. 

2.  Surface  markings : 

a.  The  conspicuous,  thickened   protuberance  at  one 

end,  the  caruncle,  a  structure  occurring  in  com- 
paratively few  species. 

b.  The  string-like  raphe,  extending   from  the  hilum 

(faintly  seen  at  the  edge  of  the  caruncle)  to 
the  chalaza,  near  the  other  end. 

II.  Remove    the   testa   and  observe  the  delicate  inner 
seed  coat,  endopleura,  enclosing  the  kernel. 

III.  Split  the  kernel  longitudinally,  so  as  to  expose  the 
embryo.     Examine  under  a  dissecting  microscope,  or  with 
a  good  lens.     Draw  the  inner  surface  of  one  of  the  halves 
so  as  to  show 

1.  The  outline  and  venation  of  the  cotyledon. 

2.  The  short,  straight  radicle. 

3.  The  surrounding  endosperm  (tissue  containing  food 

material). 

IV.  Record  in  detail  what  you  have  observed.     Note 
important  differences  between  the  castor  oil  seed  and  com- 
mon bean. 

INDIAN    CORN.     Zea  Mays,  L.1 

I.  Study  closely  the  external  features  of  the  grain. 
How  do  the  two  sides  differ  ? 

1  The  grain  of  corn  is  really  a  seed-like  fruit,  in  which  the  coats  of 
fruit  and  seed  are  blended.  Specimens  for  dissecting  should  be  placed  in 
water  the  day  before  they  are  to  be  used. 


4  STUDY    OF   COMMON   PLANTS. 

II.  With  a  sharp  knife  make    a   median   longitudinal 
section  perpendicular  to  the  flat  sides  of  the  grain.     Re- 
peat the  process,  if  necessary,  until  a  good  specimen  is 
secured.     Observe  on  the  cut  surface 

1.  The  strong  external  membrane  composed  of  the  unitecU 

coats  of  the  fruit  and  seed. 

2.  The  endosperm,  a  tissue  containing  starch  and  other 

food  materials,  very  hard  in  the   dry  grain,   but 
easily  cut  in  one  that  has  lain  some  time  in  water. 

3.  The  embryo,  with  its  conspicuous  organ  of  absorp- 

tion, scutellum,  the  latter  in  close  contact  with  the 
endosperm. 
Draw  the  section. 

III.  Remove  the  entire  embryo  from  a  grain  that  has 
been   soaked.      Dissect   out    the    parts   enclosed   in   the 
scutellum.     Compare  them  with  the  same  parts  as  seen 
in  section.     Note 

1.  The  radicle  pointing  toward  the  small  end  of  the 

grain,  its  end  covered  by  the  root-sheath. 

2.  The  caulicle,  attached  to  the  scutellum,  and  termi- 

nating above  in 

3.  The  plumule. 

IV.  Take  a  series   of   transverse   sections   and   locate 
each  one  by  comparing   it  with   a  longitudinal   section. 
Repeat  this  until  you  are  perfectly  familiar  with  all  the 
parts  and  their  relative  position. 

V.  Study  a  grain  of  corn  that  has  sprouted.     What 
changes  has  the  embryo  undergone? 

VI.  Collect  as  many  varieties  of  corn  as  you  can  and 
compare  them. 


SEEDS.  O 

VII.  Study   wheat  in   the   same   way   that  you   have 
Indian  corn,  and  compare  the  structure  of  the  two  grains. 
Compare  oats  with  both.1     In  what  respects  are  all  three 
alike  ?     Point  out  the  differences  between  them. 

VIII.  Write  a  full  account  of  your  observations  of 'these 
grains.     Point   out   two   important  particulars   in  which 
they  differ  from  peas  and  beans. 

SEEDS    OF   WHITE   PINE.     Pinus  Strobus,  L. 

I.  Observe  all  the  external  features.     Draw  in  outline  a 
perfect  specimen.     Compare  the  seeds  of  Austrian  pine  or 
Norway  spruce. 

II.  Remove  the  testa,  exposing  the  kernel  enclosed  in 
the  delicate  inner  seed  coat. 

III.  Make  both  longitudinal  and  transverse  sections  of 
the  kernel.     Notice 

1.  The  form  and  position  of  the  embryo. 

2.  Around  this  the  white,  oily  endosperm.     Draw. 

IV.  Remove    the    embryo   and   examine  under  a  good 
lens.     How  do   the  two  ends  differ?     How  many  coty- 
ledons are  there  ? 

V.  Write  a  complete  description.     In  what  important 
particulars  does  the  seed  of  the  pine  differ  from  those 
previously  studied? 

PHYSIOLOGY    OF    SEEDS. 
Storage  of  Food. 

I.    Cut  through  one   of   the    cotyledons  of   a  common 
bean   and   scrape    the    exposed   surface    lightly  with  the 

1  Cf.  Arthur,  Barnes,  and  Coulter,  Plant  Dissection,  pp.  179,  180. 


O  STUDY    OF    COMMON    PLANTS. 

point  of  a  knife.  Mount  in  water  a  very  small  portion 
of  the  powder  thus  obtained,  and  examine  under  a  com- 
pound microscope,  first  with  the  low,  and  afterward  with 
the  high  power. 

1.  Numerous  minute  bodies  are  seen  in    the   field   of 

the  microscope.  These  are  grains  of  bean  starch.1 
Are  they  all  of  the  same  size  ?  Of  the  same 
shape  ?  Draw  two  or  three  of  them. 

2.  Focus  carefully  and  study  their  structure.     Are  they 

homogeneous  ?  Compare  different  specimens  in 
regard  to  this  point. 

3.  Run  a  small  drop  of  iodine  solution  under  the  cover 

glass  and  observe  the  effect.  Notice  from  the 
outside  how  far  the  reagent  has  advanced,  then 
examine  that  part  of  the  slide  under  the  micro- 
scope, and  see  how  differently  the  starch  granules 
look  after  the  iodine  has  acted  upon  them. 

II.  Mount  in  the  same  way  a  bit  of  wheat  flo.ur  taken 
from  the  inside  of  a  grain  of  wheat. 

1.  How  do  the  starch  grains  compare  with  those  of  the 

bean  in  form,  size,  and  structure  ?  Are  the  grains 
of  wheat  starch  of  uniform  size  ? 

2.  Touch  the  cover  glass    lightly  with  a  needle  until 

some  of  the  largest  grains  roll  over.  What  is  their 
shape  ?  Draw  a  few  grains  in  different  positions 
so  as  to  represent  what  you  find  to  be  charac- 
teristic. 

3.  Test  with  iodine  solution. 

III.  Examine   corn  starch   obtained  in  the  same  way 
from  a  grain  of  Indian  corn. 

1  Useful  suggestions  for  the  microscopical  examination  of  starch  are 
given  by  Strasburger,  Practical  Botany,  pp.  4-15. 


SEEDS.  7 

1.  Compare  the  grains  of  corn  starch  with  those  of  the 

bean  and  wheat.     Draw. 

2.  Test  with  iodine  solution. 

IV.  Cut  a  grain  of   oats  in  two,  obtain  some  of   the 
starch  as  directed  in  the  preceding  cases,  and  examine 
microscopically.     The  compound  grains  of  starch  present 
a  widely  different   appearance    from   the   simple  ones  of 
Indian   corn,   wheat,   and   beans.     Study   their   structure 
carefully,  and  draw  one  or  more.     Test  with  iodine. 

From  this  and  preceding  observations  what  do  you  con- 
clude in  regard  to  the  usual  form  and  structure  of  starch  ? 
What  as  to  its  reaction  with  iodine  ? 

V.  Cut  a  sunflower  akene  in  two,  and  remove  a  small 
portion  of   the  endosperm.     Mount   in  water  and  apply 
slight  pressure  to  the  cover  glass.     Under  the  compound 
microscope  numerous  highly  refractive  drops  of  oil  will  be 
seen  coming  out  of  the  broken  tissue.     Focus  carefully  on 
an  oil  drop,  and  observe  its  sharply  denned  border.     What 
changes  does  it  undergo  as  the  focus  is  altered? 

Various  other  oily  seeds,  such  as  those  of  the  squash, 
tomato,  pine,  English  walnut,  etc.,  may  be  studied  in  the 
same  way.  Enough  of  these  should  be  examined  to  ensure 
familiarity  on  the  part  of  the  student  with  the  appearance 
of  fatty  oil  under  the  microscope. 

VI.  Soak  a  date  seed  in  water  a  day  or  more  until  it 
can  be  cut  easily.     Pare  off  a  portion  of  it  with  a  knife  or 
scalpel,  so  as  to  expose  a  smooth,  even  surface,  and  then 
with  a  razor  make  extremely  delicate  sections  of  the  endo- 
sperm.    Mount  some  of  these  in  glycerine,  and  others  in 
Schulze's  solution.     Microscopic   examination  shows  that 
the    date   seed  consists  chiefly  of   the  greatly  thickened 
walls  of  the  cells  that  compose  its  substance.     Watch  the 


8  STUDY   OF   COMMON   PLANTS. 

action  of   Schulze's   solution.     The  blue  color  that  pres- 
ently appears  indicates  cellulose. 

VII.  Examine  similar  sections  of  a  coffee  seed  prepared 
and  mounted  in  the  same  way.     Notice  how  the  cell  walls 
differ  from  those  of  the  date  seed. 

VIII.  Remove  the  testa  of  a  castor  oil  seed,  and   cut 
a  few  thin  sections  from  the  endosperm.     Mount  in  pure 
glycerine,  and  examine  with  the  high  power. 

1.  The  sections  show  (best  on  the  edges  where  they  are 

very  thin)  the  cells  of  the  endosperm  filled  with 
numerous  rounded  bodies.  These  are  aleurone 
grains.  They  are  of  frequent  occurrence  in  oily 
seeds,  and  constitute  an  important  food  substance. 

2.  Draw  a  cell  with  its  contents.     Examine  the  aleurone 

grains  closely,  and  see  if  you  can  detect  any  struct- 
ure. The  small  rounded  body  most  frequently 
seen  at  one  end  of  the  aleurone  grain  is  called  a 
globoid. 

3.  Run  a  drop  of  water  under  the  cover  glass  and  watch 

the  effect.  Some  of  the  aleurone  grains  presently 
show,  besides  the  rounded  globoid,  an  angular 
crystalloid. 

Draw  again  a  cell  with  its  contents  so  as  to  show  the 
changes  that  have  taken  place. 

4.  After  the  water  has  had  sufficient  time  to  act  on  the 

cell  contents,  it  is  evident  that  they  are  becoming 
disorganized,  and  drops  of  oil  are  seen  to  have 
passed  out  of  the  section. 

NOTE.  —  It  is  important  that  all  of  these  features  should  be  sat- 
isfactorily made  out  before  proceeding  farther.  It  may  be  neces- 
sary to  prepare  a  considerable  number  of  slides,  and  possibly  will 
require  several  hours.  The  essential  fact  is  that  in  the  castor  oil 
seed  two  sorts  of  food  are  stored :  one  non-nitrogenous,  in  the 


SEEDS.  9 

form  of  fatty  oil;  the  other  nitrogenous,  in  the  form  of  aleurone. 
We  shall  find  the  same  association  of  nitrogenous  and  non-nitrog- 
enous food  substances  in  other  seeds. 

IX.  Prepare  sections  of  the  endosperm  of  a  flax  seed, 
and,  as  before,  examine  some  in  glycerine  and  others  in 
water.     How  do  the  aleurone  grains  compare  in  size,  form, 
and  structure  with  those  of  the  castor  oil  seed?1 

X.  Make  a  transverse  section  of  a  grain  of  wheat  that 
has  lain  in  water  a  few  hours,  cutting  it  in  such  a  way  that 
the  section  will  show  the  coats  of  the  grain  and  a  portion 
of  the  endosperm.     Mount  in  water.     Notice 

1.  The  large  cells  making  up  most  of  the  endosperm. 

What  do  they  contain? 

2.  Outside  of  these  a  layer  of  cells,  rectangular  in  sec- 

tion, containing  aleurone. 

3.  The   behavior  of   the   substances   contained   in   the 

different  cells  when  iodine  is  applied.  Draw  a 
portion  of  the  section. 

4.  The    arrangements    for    protection   of    the   embryo, 

together  with  its  food  supply,  by  means  of  the 
united  fruit  and  seed-coats.  [The  former  consists 
of  several  layers  of  cells  with  strongly  thickened 
walls,  the  latter  of  two  very  thin  layers  imme- 
diately outside  the  cells  that  contain  aleurone. 
Tangential  sections  treated  with  sulphuric  acid, 
compared  with  the  transverse  sections,  will  make 
the  structure  plain.] 

XL  Record  in  full  what  you  have  ascertained  regarding 
reserve  materials  and  their  storage  in  seeds.  What  are 
the  different  kinds  of  non-nitrogenous  food  substances  thus 

1  Cf.  Frank,  Lehrbitch  der  Pflanzenphysioloyie,  p.  158. 


10  STUDY   OF   COMMON   PLANTS. 

far  met  with  ?     How  are  they  recognized  ?     Mention  cases 
where  you  have  found  them  associated  with  aleurone.1 

Protection. 

I.  Examine  an  orange  with  reference  to  the  protection 
of  the  embryos.     Make  a  transverse  section  of  the  fruit, 
and  note  carefully  all  the  protective  arrangements. 

II.  Study  an  apple  in  the  same  way. 

III.  Compare    a    number   of  commercial    "nuts";    e.g. 
almond,  chestnut,  peanut,  hickory  nut,  Brazil  nut.     Which 
are  the  most  effectually  protected  ?     How  do  they  compare 
with  other  fruits  in  this  respect  ? 

IV.  Make  a  transverse  section  of  a  grain  of  Indian  corn 
and    examine    the    pericarp   microscopically.     Notice   the 
multiplication  of  thick-walled  cells  and  their  arrangement. 
Draw. 

V.  After  observing  as  many  other  seeds  as  are  obtain- 
able, summarize  your  observations  of  the  ways  in  which 
the  embryo  is  protected  against  mechanical  injuries,  wet- 
ting, destruction  by  animals,  attacks  of  fungi,  etc.     Are 
any  that  you  have  examined  poorly  protected  ? 2 

Dispersal. 

I.  Examine  the  seeds  of  common  milkweed,  Asclepias 
Cornuti,  Decaisne.    Compare  those  of  the  trumpet  creeper, 
Tecoma  radicans,  Juss.      Make  an  outline  sketch  of  both. 

II.  Study  as  many  as  can  be  obtained  of  the  following : 
Seeds  of  willow  or  poplar;  fruits  of  elm,  birch,   maple, 
ash,  clematis,  hop  tree,  Ptelea,  iron-wood,  Ostrya  or  Carpi- 

1  Cf.  Sachs,  Physiology  of  Plants,  pp.  323-340. 

2  Cf.  De  Candolle,  Origin  of  Cultivated  Plants,  p.  395. 


SEEDS.  11 

nus,  thistle,  dandelion,  wild   lettuce,  cotton   grass,  Erio- 
phorum. 

In  the  air  of  a  still  room  see  whether  any  of  these  fall 
perpendicularly  from  a  height  of  a  few  feet.  What  is  the 
case  when  the  air  is  disturbed  by  fanning? 

III.  Examine  the  fruits  belonging  to  some  or  all  of  the 
following  genera :  Agrimonia,  Geum,  Desmodiurn,  Circaea, 
Galium,  Lappa,  Xanthium,  Echinospermum,  Cynoglossum, 
Bidens,  Cenchrus. 

Describe  the  various  appendages  and  compare  them  as 
to  their  efficiency. 

By  means  of  a  thread  suspend  weights  to  one  of  the 
hooked  appendages  of  the  burdock  and  ascertain  how 
great  a  weight  the  hook  will  bear. 

IV.  Write  out  a  list  of   fruits   attractive  to   animals, 
taking  care  to  include  only  such  as  you  have  yourself 
observed. 

V.  Discuss  any  other  arrangements  for  dispersal  of  seeds 
with  which  you  are  familiar.     Read  one  or  more  of  the 
references  given  below.1 

RELATIONSHIPS   INDICATED    BY   SEEDS. 

I.  Examine  seeds  of  mustard,  radish,  cabbage,  and 
other  cruciferous  plants,  comparing  them  with  reference 
to  their  form  and  size,  form  and  position  of  the  embryo, 
nature  of  reserve  material,  and  other  points  of  difference 
and  resemblance.  The  study  will  be  facilitated  by  com- 
paring seeds  that  have  been  planted  two  or  three  days. 

1  Darwin,  Origin  of  Species,  Chap.  XII ;  Lyell,  Principles  of  Geology, 
Vol.  II,  Chap.  XL;  Hill,  Am.  Nat.,  1883,  pp.  811,  1028;  Hildebrand, 
Verbreitunysmittel  der  PJlanzen  ;  AYallace,  Darwinism. 


12  STUDY   OF    COMMON    PLANTS. 

Draw  and  describe  the  various  parts  of  some  of  the 
different  seeds. 

II.  Compare  in  the  same  way  peas,  beans,  lima  bean, 
lupine,  and  peanut.     Are  they  essentially  alike  in  struct- 
ure ?     Mention  points  of  difference. 

III.  Compare   seeds   of   squash,  pumpkin,  watermelon, 
muskmelon,  cucumber,  and  gourd. 

IV.  Compare  seeds  of  tomato,  egg  plant,  pepper,  stra- 
monium, and  hyoscyamus. 

V.  Compare  the  seed-like  fruits  of  sunflower,  dandelion, 
thistle,  lettuce,  and  salsify. 

In  all  the  groups  thus  studied  ascertain  whether  the 
seeds  are  more  alike  than  different.  Sections  should  be 
made  and  drawings  introduced  wherever  they  are  needed 
to  render  the  descriptions  more  intelligible.  Some  of  the 
groups  may  be  omitted  if  necessary,  but  the  observations 
should  be  thorough  and  complete  as  far  as  they  are 
carried. 

SPECIAL   STUDIES.1 

I.    Polyembryony  in  the  genus  Citrus.     This  requires 

an    extended   comparison    of    seeds   of   different 

varieties  of  orange,  lemon,  and  other  citrus  fruits. 

II.    Arillate  seeds.     A  study  of  the  seeds  of   Celastrus 

scandens  and  other  arillate  species. 

III.    Relation  of   the  embryo  to  the  reserve    material. 
Arrangements  that  favor  a  prompt  supply  of  food 

1  A  few  subjects  for  special  study  are  given  in  connection  with  this 
and  other  exercises  simply  as  examples  of  many  that  will  naturally 
suggest  themselves.  In  most  cases  the  studies  suggested  require  inde- 
pendent investigation,  while  others,  such  for  example  as  number  IV,  give 
opportunity  for  reading  and  reporting  on  papers  of  special  interest,  par- 
ticularly those  in  recent  periodical  literature. 


SEEDS.  13 

to  the  embryo  in  early  stages  of  germination. 
Cf.  Haberlandt,  Physiologische  Pflanzenanatomie, 
p.  288  et  seq. 

IV.    Peculiar   cases  of   plant   dissemination.     Cf.  Ber- 

thoud,  Botanical  Gazette,  XVII  (1892),  p.  321. 
V.  Identification  of  species  by  means  of  seeds.  An 
interesting  application  will  be  found  in  the  deter- 
mination of  weed  seeds  of  frequent  occurrence  in 
grass  and  clover  seed.  Cf.  Beal,  Grasses  of  North 
America,  I,  p.  215. 

REVIEW    AND    SUMMARY. 

The  seeds  we  have  studied  have  been  selected  from 
three  great  classes  of  plants.  To  the  first  class  belong 
the  bean,  castor  oil,  and  other  plants,  the  seeds  of  which 
have  two  cotyledons ;  to  the  second,  wheat,  Indian  corn, 
and,  in  general,  all  plants  with  one  cotyledon ;  and  to  the 
third,  pines  and  their  allies,  many  of  which  have  more 
than  two  cotyledons.  The  distinctions  between  these 
classes  are  in  many  respects  fundamental,  so  that  an 
examination  of  the  seed  of  a  given  plant  is  generally  suffi- 
cient to  enable  us  to  determine  its  class  in  the  vegetable 
kingdom.1 

Furthermore,  we  have  found  that  there  are  more  re- 
stricted groups  of  plants,  called  families,  the  seeds  of 
which  are  in  many  cases,  though  not  in  all,  so  nearly 
identical  in  structure  as  to  indicate  at  once  their  family 
relationship.  The  squash,  melon,  and  cucumber  belong 
to  one  of  these  families ;  the  tomato,  egg  plant,  and  stra- 
monium to  another,  and  so  on.  We  conclude,  therefore, 

1  Seedless  or  "  cryptogamic  "  plants  will  be  studied  later.  What  is 
said  in  the  present  chapter  and  those  immediately  following  applies  to 
the  higher  or  seed-bearing  plants,  including  Gymnosperms. 


14  STUDY   OF   COMMON   PLANTS. 

that  the  structure  of  seeds  is  an  important  factor  in  the 
determination  of  relationship.1 

This  being  the  case,  it  becomes  necessary  to  formulate 
certain  general  conceptions  of  form  and  structure,  and  to 
Morphology  adopt  descriptive  language  by  which  they  may 
of  seeds,  ke  expressed  with  clearness.2 

The  essential  parts  of  a  seed  are  the  protective  coats 
and  the  embryo  with  its  store  of  food.  The  seed-coats 
commonly  show  a  division  into  an  external, 
hard,  often  colored,  layer,  the  testa,  and  an  in- 
ternal, more  delicate  one,  the  endopleura;  the  former 
term,  however,  is  frequently  employed  to  designate  the 
coats  collectively.  In  many  species  the  endopleura  is 
wanting.  Externally  the  testa  may  be  smooth  and  pol- 
ished, as  is  the  case  with  the  seed  of  the  castor  oil  plant, 
or  it  may  be  covered  with  hairs,  as  cotton  seeds  are,  or, 
again,  it  may  be  extended  into  a  wing,  like  that  belong- 
ing to  the  seeds  of  the  catalpa,  and  various  other  modifi- 
cations may  occur,  having,  as  a  rule,  a  direct  relation  to 
protection  or  dissemination.  An  additional  coat,  usually 
colored  and  fleshy,  known  as  the  aril,  is  rarely  present. 

The  parts  of  the  embryo  are  the  radicle,  cotyledons,  and 
plumule.     As  we  have  seen,  it  may  have  one,  two,  or  sev- 
eral cotyledons,  and   accordingly  is  said  to  be 
monocotyledonous,  dicotyledonous,  or  polycoty- 
ledonous.     The  embryo  varies  greatly  in  different  species 
as   regards    form,   position,   and   size,   being    straight   or 
curved ;  occupying  the  whole  space  within  the  seed-coats, 
or  only  a  small  portion  of  it ;  the  cotyledons  alike  or  dif- 

1  See,  for  example,  Rowlee,  Bulletin  of  the  Torrey  Botanical  Club, 
XX  (1893),  p.  1,  and  Rolfs,  Botanical  Gazette,  XVII  (1892),  p.  33. 

2  For  a  more  extended  treatment  of  the  morphology  of  seeds  cf .  Gray, 
Structural  Botany. 


SEEDS.  15 

fering  in  size  or  shape,  and  so  on ; l  but  these  peculiarities 
are  generally  constant  and  characteristic  in  the  species,  or 
group  of  species,  in  which  they  occur.  Whatever  the 
form  and  position  of  the  embryo,  the  radicle  points  towards 
the  micropyle. 

Food  materials  of  various  kinds  are  stored  up  for  the 
use  of  the  plantlet  during  germination.     If  the  tissue  con- 
taining  such   reserve  materials   surrounds   the 
embryo,  it  is  called  the  endosperm,  or,  using  an 
old  phraseology,  the  seed  is  said  to  be  albuminous.     If,  on 
the  contrary,  the  reserve  materials  are  stored  within  the 
embryo   itself,    even  if   they   are    of   precisely   the   same 
nature,  the  seed  is  said  to  be  without  endosperm,  or  exal- 
buminous.2     The  terms  are  not  well  chosen,  but  have  be- 
come so  fixed  as  to  render  it  necessary  to  recognize  them. 

Certain  structural  peculiarities  are  intimately  connected 
with  the  developmental  history  of  seeds.  They  are  at- 
tached to  the  mother  plant  by  a  minute  stalk  _ 

,  ,    Hilnm,  rapne, 

through  which  nutritive  materials  are  conveyed  chalaza,  mi- 
during  their  period  of  growth,  but  from  which  cr°Pyle- 
they  break  away  at  maturity,  leaving  a  scar  called  the 
hilum,  such  as  is  plainly  seen  on  the  common  bean.  From 
the  hilum,  in  the  great  majority  of  cases,  extends  a  fine, 
fibrous  bundle,  the  raphe,  like  that  of  the  castor  oil  seed, 
either  the  entire  length  of  the  seed,  or  for  a  shorter  dis- 
tance, ending  in  a  point,  the  so-called  chalaza,  where  the 
seed  coats  cohere  with  each  other  and  with  the  parts 
within.  The  raphe  is  simply  a  continuation  of  the  stalk 
through  which  food  materials  were  carried  to  the  develop- 
ing seed,  the  chalaza  being  the  point  where  the  materials 

1  Cf.  Lubbock,  Seedlings. 

2  For  the  rare   cases  in  which  a  distinction  must  be  made  between 
endosperm  and  perisperm,  see  Gray,  Structural  Botany,  p.  310. 


16  STUDY    OF    COMMON   PLANTS. 

were  distributed  to  the  interior  of  the  seed.  The  hilum  is 
in  almost  all  cases  a  conspicuous  feature,  readily  seen  by 
the  unaided  eye,  or  with  the  help  of  a  lens.  The  chalaza 
and  raphe,  on  the  contrary,  are  frequently  obscured  by 
the  growth  of  the  seed-coats.  The  micropyle  is  the  open- 
ing between  the  seed-coats,  readily  seen  in  early  stages  of 
development,  but  often  not  easily  recognized  from  the  out- 
side of  the  mature  seed.  Its  position  is  most  readily 
determined  by  opening  the  seed  and  rinding  the  radicle, 
which,  as  already  said,  points  toward  the  micropyle. 

The  form  of  the  seed  is  also  determined  largely  by  the 
direction  of  growth  of  the  ovule.  In  the  majority  of 
cases,  of  which  the  castor  oil  seed  is  a  good 
terminedby-  example,  the  developing  ovule  turns  upon  its 
direction  of  longitudinal  axis  in  such  a  way  as  to  take  an 
inverted  position,  so  that  in  the  mature  seed 
the  hilum  and  micropyle  are  close  together,  the  chalaza  at 
the  opposite  end,  and  the  raphe  running  the  whole  length 
of  the  seed.  Such  seeds  are  said  to  be  anatropous. 
Others,  as,  for  example,  the  seeds  of  stramonium,  are 
simply  much  curved,  bringing  both  chalaza  and  micropyle 
near  the  hilum,  one  on  either  side  of  it.  This  is  the 
so-called  campylotropous  form.  In  comparatively  few 
species,  of  which  buckwheat  is  an  example,  the  axis  of 
the  ovule  remains  straight  throughout  its  development, 
and  the  seed  is  said  to  be  orthotropous.  Modifications, 
particularly  of  the  first  and  second  forms,  are  of  frequent 
occurrence.  Cf.  Gray,  Structural  Botany,  pp.  278,  279. 

Physiologically,  seeds  present  many  points  of  interest. 
The  arrangements  for  dispersal,  for  protection,,  and  for 
Physiological  the  support  of  the  embryo  in  germination  are 
adaptations,  among  the  most  important. 

A  species  generally  has  a  better  chance  of  survival  if 


SEEDS.  17 

the  seeds  are  conveyed  to  some  distance  from  the  plant  on 
which  they  are  produced.  By  this  means  they 
are  less  likely  to  come  into  as  close  competition 
with  each  other  as  if  they  grew  up  together  around  the 
parent  plant;  they  are  also  brought  into  other  conditions 
of  soil  and  surroundings,  and  the  chances  for  cross-fertil- 
ization are  greater,  which,  as  we  shall  see,  is  often  a 
marked  advantage.  Accordingly  it  is  found  that  a  variety 
of  structures  exist  that  are  directly  adapted  to  the  dis- 
semination of  seeds.  Thus  many  seeds  are  distributed 
by  the  action  of  the  wind.  These  are  most  frequently 
light  in  weight  and  provided  with  appendages  in  the  form 
of  wings  or  hairs,  such  as  those  of  the  catalpa,  poplar, 
milkweed,  and  many  others.  Seeds  distributed  by  animals 
are  often  concealed  within  brightly  colored  or  otherwise 
attractive  fruits ;  in  other  cases  they  are  provided  with 
hooks  or  other  appendages  by  which  they  become  attached 
to  the  wool  or  hair  of  various  animals,  and  the  seeds  of 
many  water-loving  plants  are  carried  in  the  mud  that 
adheres  to  the  feet  of  aquatic  birds.  The  seeds  of  still 
others  are  washed  by  oceanic  currents  to  the  shores  of 
distant  islands  or  continents,  and,  finally,  the  agency 
of  man,  both  intentional  and  unintentional,  becomes  a 
potent  factor  in  the  distribution  of  plants. 

By  these  and  other  agencies  the  forms  that  constitute  the 
vegetation  of  the  earth  have  come  to  occupy  the  places  in 
which  we  now  find  them,  and  it  becomes  for  every  species 
that  we  meet  a  fascinating  and  often  intricate  problem  to 
endeavor  to  ascertain  how  it  came  to  be  where  it  is. 

It  is  plain  that  from  the  time  they  leave  the  mother  plant 
to  the  time  of  germination,  seeds  are  exposed 
to  numerous  dangers,  and  that  they  require  pro- 
tection.    This  is  afforded  in  part  by  the  shape  of  the  seed, 


18  STUDY   OF   COMMON   PLANTS. 

most  frequently  a  combination  of  strong  arches,  by  which 
the  danger  of  crashing  is  lessened;  in  part  by  the  hard 
testa,  which  sometimes  has  a  compact,  polished  exterior 
that  resists  the  entrance  of  water  and  germs  ;  and  in  some 
cases  by  bitter  or  otherwise  distasteful  substances  stored 
up  in  the  seed.  In  addition  to  these  means  of  protection 
the  embryo  is  often  securely  packed  in  the  midst  of 
abundant  endosperm,  and  not  infrequently  still  other  pro- 
vision is  made  for  its  safety. 

Microscopic  examination  of  a  seed  shows  the  presence 
of  one  or  more  kinds  of  reserve  materials.  As  a  rule, 
Reserve  starch,  or  some  other  non-nitrogeneous  sub- 
materials,  stance,  is  associated  with  aleurone  or  its  equiva- 
lent, thus  supplying  all  the  essential  food  elements.  Oil, 
as  a  condensed  form  of  food,  is  largely  employed  in  small 
seeds  and  those  that  are  transported  by  the  wind,  since  by 
the  use  of  this  material  greater  lightness,  volume  for 
volume,  is  secured  than  if  starch  were  employed.  Cellu- 
lose takes  the  place  of  starch  or  oil  in  the  date  and  some 
other  seeds,  which,  as  Haberlandt  has  pointed  out,  are  in 
this  way  rendered  less  liable  to  decay  and  the  attacks  of 
animals  during  their  long  period  of  germination.1  It  is 
also  seen  upon  the  careful  study  of  almost  any  seed  that 
the  reserve  materials  are  so  placed  as  to  be  ready  for 
immediate  use  when  wanted,  either  lying  in  the  cells  of 
the  embryo  itself  or  packed  closely  around  it,  and  there 
brought  into  immediate  relation  with  its  absorbing  tissue. 

Still  other  physiological  adaptations  will  be  apparent  as 
a  greater  number  of  seeds  are  examined  and  their  struct- 
Other  adapta-  ural  peculiarities  brought  to  light.  As  an  exam- 
tions,  pie  may  fog  mentioned  the  fact  that  anatropous 

seeds  by  curving  upon  themselves  during  the  early  stages 
1  Physiologische  Pflanzenanatomie,  p.  285  et  seq. 


SEEDS.  19 

of  their  development  bring  the  micropyle  into  such  a 
position  as  to  favor  the  entrance  of  the  pollen  tube. 
Again,  the  hairy  appendages  of  numerous  achenia,  such 
as  those  of  the  dandelion  and  related  plants,  are  so  placed 
as  to  bring  the  radicle  on  the  lower  side  as  the  object 
alights  on  the  surface  of  the  ground.1  Such  adaptations 
are  of  so  constant  occurrence  that  the  student  can  hardly 
fail  to  receive  the  impression,  in  general  a  correct  one, 
that  the  simplest  structural  facts  are  likely  to  have  some 
important  physiological  significance.  On  the  other  hand, 
there  are  numerous  cases  of  "  accidental "  peculiarities,  for 
which  no  reason  is  manifest,  and  which  at  present  are  not 
explained. 

1  Cf.  Rowlee,  I.e. 


20  STUDY    OP   COMMON   PLANTS. 


II.     GROWTH  OF  PLANTS   FROM   THE   SEED. 

MATERIAL    REQUIRED. 

Seedlings  of  the  common  bean,  pea,  sunflower,  white  mustard,  flax, 

and  hemp,  from  one  to  four  weeks  old.1 
Seedlings  of  Indian  corn  and  wheat  of  various  ages. 
Pine  seedlings  from  a  few  weeks  to  a  few  months  old. 
Seeds  of  squash  and  other  cucurbits  in  early  stages  of  germination. 

I.  Take  seedlings  of  different  ages  of  the  plants  named 
in  the  first  list  above.  Wash  the  roots  and  let  them  stand 
in  a  dish  of  water  to  prevent  drying.  Compare  them  and 
satisfy  yourself  as  to  the  following  points : 

1.  Do  they  all  have  a  taproot? 

2.  Do  they  all  have  a  hypocotyl,  i.e.  a  stem  supporting 

the  cotyledons? 

3.  How  do  the  cotyledons  of  the  different  plants  differ 

a.  As  to  form  and  size  ? 

b.  In  function  ?     Have  any  of  them  wholly  lost  their 

function  as  foliage  leaves?  Are  there  any 
apparently  transitional  forms,  as  if  this  function 
were  partially  lost? 

4.  How  does  the  pea  differ  from  the  sunflower  in  the 

time  of  unfolding  the  proper  foliage  leaves  ?     Can 

1  The  seeds  should  be  sown  at  intervals  of  a  few  days,  some  in  sand, 
others  in  moist  (not  wet)  sawdust,  and  still  others  on  folds  of  damp 
blotting  paper  under  a  bell-jar.  There  should  be  three  or  four  lots  of  as 
many  different  ages.  Pine  seedlings,  which  are  rather  difficult  to  raise, 
may  be  obtained  from  nurseries. 


GROWTH   OF   PLANTS   FKOM   THE   SEED.  21 

you  suggest  any  reason  for  this  difference?     How 
do  the  other  seedlings  compare  in  this  respect? 

II.  Compare  the  seedlings  of  Indian  corn  and  wheat 
that  have  attained  the  height  of  several  inches. 

1.  Describe    the    cotyledon.     Has    it    undergone    any 

change  during  the  process  of  germination  ? l 

2.  Is  there  a  taproot? 

3.  Mention  all  the  points  in  which  the  two  plants  are 

alike  ;  those  in  which  they  differ. 

III.  Compare   the   seedlings    of   the    Indian    corn   and 
wheat  with  those  of  the  pea,  bean,  etc.,  previously  studied. 
Point  out  all  the  essential  differences,  noting  especially 

1.  Number  of  cotyledons. 

2.  Venation  of  foliage  leaves. 

3.  Position  and  form  of  leaves. 

4.  Presence  or  absence  of  a  persistent  taproot. 

IV.  Examine  seedlings  of  the  white  pine  or  other  species 
of  pine.     In  what  important  feature  do  they  differ  from 
any  of  the  young  plants  thus  far  studied? 

V.  Summarize   your  observations    and   show   how  the 
class    to  which  a  plant  belongs  may  be  determined   by 
inspection  of  the  seedling.2 

VI.  Comparing  the  seedlings  of  different  dicotyledonous 
plants  (beans,  sunflower,  etc.),  ascertain  whether  any  of 
them  have  the  two  cotyledons  unlike  in  size  or  shape.     Is 
there  anything  to  indicate  that  the  form  of  the  embryo 
is  determined  by  that  of  the  seed  ?  3 

1  The  protective  sheath  is  regarded  as  a  part  of  the  cotyledon,  while 
the  other  part,  the  scutellum,  remains  in  the  grain.     Cf.  Lubbock,  Seed- 
lings, IT,  p.  587. 

2  Cf .  Gray,  Structural  Botany,  Chap.  II. 

3  Lubbock,  Seedlings,  I,  pp.  30-34,  75-77. 


22  STUDY    OF    COMMON   PLANTS. 

VII.  Notice    the    way    the    different    seedlings    break 
through  the  ground.     Do  those  of  all  the  dicotyledonous 
plants  behave  alike?     How  do  they  compare  with  those 
of  Indian  corn  and  other  monocotyledons  ? 1 

VIII.  Examine  seedlings  of  squash,  melon,  or  cucum- 
ber, comparing  specimens  that  are  just  rupturing  the  testa 
with  older  ones.     Observe  the  position  and  structure  of 
the  "  peg,"  and  the  way  it  aids  in  throwing  off  the  seed- 
coats.2 

IX.  Ascertain  whether  direction  of  growth  is  affected 
by  external  conditions. 

1.  Compare  mustard  or  other  seedlings  grown  in  the 

dark  with  others  growing  in  front  of  a  window. 

2.  Turn  on  their  sides  some  of  the  pots  with  seedlings 

a  few  inches  high,  and  after  a  day  or  two  notice  the 
result. 

3.  Observe  the  effect  of  slow  change  of  position  in  neu- 

tralizing geotropism  and  heliotropism.3 

X.  Take  up  a  seedling  of  wheat  about  two  weeks  old, 
and  examine  the  grain. 

1.  Notice   how  it  differs   from   a   grain   that   has   not 

sprouted. 

2.  Remove  a  small  portion  of  the  endosperm  and  ex- 

amine under  a  high  power  of  the  microscope. 
Compare  the  starch  grains  with  those  of  wheat 
that  has  not  sprouted.  What  changes  have  taken 
place  ?  Draw  some  of  the  grains  that  show  "  cor- 
rosion." 

1  Darwin,  Power  of  Movement  in  Plants,  p.  77  et  seq. 

2  Darwin,  I.e.,  p.  102. 

3  For  this  purpose  an  instrument  known  as  a  klinostat  is  employed. 
Cf.  Goodale,  Physiological  Botany,  p.  408;  Sachs,  Physiology  of  Plants, 
p.  684.     Less  expensive  apparatus  is  easily  devised. 


GROWTH   OF   PLANTS   FROM   THE   SEED.  23 

3.  Examine  in  the  same  way  starch  from  the  endosperm 
of  a  corn  seedling  that  has  attained  several  inches 
in  height. 

XI.  Write  a  detailed  account  of  the  phenomena  of 
germination  as  far  as  you  have  observed  them. 

SPECIAL   STUDIES. 

I.  How  seedlings  break  through  the  ground.  A 
further  comparison,  including  the  study  of  as 
many  species  as  practicable. 

II.    Results  of  planting  certain  seeds  wrong  side  up.1 

III.  Results  of  removal  of  cotyledons  at  an  early  stage 

of  growth. 

IV.  Whether  detached  embryos  are  capable  of   germi- 

nation. 

V.    Conditions  most  favorable  to  germination. 
VI.    Length  of  time  that  seeds  retain  their  vitality. 

VII.    How  far  seedlings  of  the  same  family  are  alike  in 
structure  and  habits. 

VIII.  Changes  capable  of  demonstration  under  the  micro- 
scope that  take  place  in  reserve  materials  during 
germination. 

REVIEW   AND    SUMMARY. 

In  our  study  of  seedlings  we  have  found  that  the  same 
parts  are  present  that  were  observed  in  the  seed,  but 
marked  changes  have  taken  place  in  size,  position,  texture, 
and  other  particulars.  The  distinctive  features  of  the 

1  Cf.  Darwin,  I.e.,  pp.  103,  104. 


24  STUDY   OF   COMMON   PLANTS. 

great  classes,  however,  are  as  strongly  marked  as  they 
were  in  the  seed,  and  each  class  exhibits  in  its  seedlings 
characteristic,  though  not  always  distinctive,  habits. 

The  radicle  of  dicotyledonous  seedlings  elongates  and 
extends  downwards  as  the  primary  root,  and  at  the  same 

Dicot  ledo  ^me  *n  mos^  sPecies  grows  upward,  forming  the 
nous  seed-  "  hypocotyl,"  at  the  upper  extremity  of  which 

the  cotyledons  are  borne.  In  some  species,  as 
in  the  pea,  the  hypocotyl  is  wanting,  or  is  extremely  short, 
the  cotyledons  remaining  in  the  ground  instead  of  being 
lifted  into  the  air.  In  such  cases  a  rapid  development  of 
the  "epicotyl,"  or  first  internode  of  the  plumule,  takes 
place,  thus  securing  to  the  young  leaves  as  they  unfold 
full  exposure  to  air  and  light.  The  hypocotyl  (or,  if  this 
is  wanting,  the  epicotyl)  breaks  through  the  ground  in  the 
form  of  an  arch,  an  arrangement  for  the  protection  of  the 
delicate  growing  point.1 

Monocotyledonous  seedlings  exhibit  considerable  variety 
among  themselves,  although  several  pretty  distinct  types 

may  be  recognized.  In  the  grasses  the  scutel- 
nous  seed-  lum,  which  represents  a  part  of  the  cotyledon, 
lmgSl  remains  enclosed  in  the  grain,  and  the  straight 

plumule  is  erect,  instead  of  arched,  as  it  breaks  through 
the  ground.  In  many  other  species,  as  for  example  the 
date  palm,  a  peculiar  modification  of  this  mode  of  germi- 
nation is  seen.  As  before,  a  part  of  the  cotyledon  remains 
in  the  seed  as  an  organ  of  absorption,  but  the  other  end 
elongates  and  grows  downward,  forming  a  sheath  from 
which  the  first  leaf  afterward  emerges.2  A  more  or  less 
conspicuous  primary  root  may  be  present,  as  in  Indian 

1  Cf.  Darwin,  Poiver  of  Movement  in  Plants,  pp.  87,  88. 

2  See  figures  of  palm  seedling,  Goebel,  Classification  and  Special  Mor- 
phology of  PI  a  Jits,  p.  432. 


GROWTH   OF   PLANTS   FROM  THE   SEED.  25 

corn,  or  it  may  be  hardly  distinguishable  from  the  secon- 
dary roots,  as  is  the  case  with  wheat. 

Seedlings  of  pines  and  their  allies  (gymnosperms),  aside 
from  the  fact  that  many  species  have  more  than  two  coty- 
ledons, can  hardly  be  said  to  possess  characters  seedlings  of 
specially  distinctive  of  their  class.  In  many  gymnosperms. 
cases  the  testa  is  carried  up  on  the  tips  of  the  cotyledons, 
and  afterwards  thrown  off  by  their  bulging  outwards.  In 
some  species  the  cotyledons  remain  under  ground. 

Cotyledons,  as  a  rule,  perform  functions  widely  different 
from  those  of  ordinary  green  leaves,  and  accordingly  pre- 
sent striking  modifications  of  form  and  structure.  n  ,  .  . 

Cotyledons 

While  in  some  cases  they  unfold  and  deport  and  their  mod- 
themselves  as  foliage  leaves,  in  others,  as  for  lficatlonSl 
example  the  pea  and  acorn,  they  have  lost  nearly  all 
resemblance  to  leaves,  and  serve  merely  as  storehouses  of 
reserve  materials ;  while  in  still  other  cases,  as  in  the  grain 
of  corn  or  wheat,  the  cotyledon  becomes  largely  an  organ 
of  absorption.  Interesting  transitional  forms  are  seen  in 
the  common  bean  and  other  plants  in  which  the  cotyle- 
dons rise  above  the  surface  and  turn  green,  but  soon  dry 
up  after  their  reserve  materials  are  exhausted.  The 
embryos  of  some  dicotyledonous  plants  produce  but  one 
cotyledon,  the  other  being  rudimentary.  A  curious  in- 
stance is  that  of  the  orange,  in  the  seed  of  which  several 
embryos  are  formed  with  cotyledons  varying  greatly  in 
size.  In  various  species  of  cacti  both  cotyledons  are  rudi- 
mentary, being  represented  by  minute  bodies  only  a  milli- 
meter or  two  in  diameter.  In  the  latter  case  the  radicle  is 
thickened  and  serves  as  a  storehouse,  the  cotyledons  be- 
come superfluous,  and  are  finally  reduced  to  insignificant 
appendages,  an  illustration  "  of  the  principle  of  compensa- 
tion or  balancement  of  growth,  or,  as  Goethe  expresses  it, 


26  STUDY  OF  COMMON  PLANTS. 

'  in  order  to  spend  on  one  side,  Nature  is  forced  to  econo- 
mize on  the  other  side.' " l  A  considerable  number  of 
seeds,  notably  those  of  certain  plants  belonging  to  the 
mustard  family,  have  one  cotyledon  larger  than  the  other, 
an  arrangement  naturally  following  the  way  the  embryo 
is  packed  in  the  seed.  These  and  various  other  peculiar- 
ities may  be  seen  in  the  embryo  before  germination,  but 
are  more  pronounced  in  the  young  seedling. 

During  germination  the  reserve  materials  stored  in  or 
around  the  embryo  are  drawn  upon  for  the  sustenance 
Chan  es  °^  ^e  seedling.  Microscopic  examination  of 
in  reserve  the  endosperm  of  a  grain  of  wheat  or  Indian 
corn,  after  the  seedling  is  well  started,  shows 
that  the  starch  granules  have  undergone  remarkable 
changes  due  to  the  action  of  a  ferment  that  gradually 
dissolves  them.  Other  reserve  materials,  such  as  oil, 
aleurone,  etc.,  undergo  similar  changes,  by  which  they 
are  fitted  for  absorption,  but  these  are  too  complicated 
to  be  discussed  in  an  elementary  work.  Those  interested 
in  the  chemistry  of  germination  should  consult  Sachs, 
Physiology  of  Plants,  and  later  articles  in  various  botan- 
ical periodicals. 

Certain  external  conditions  are  essential  to  germination. 
Of  these  the  most  important  are  (1)  a  suitable  amount  of 
Conditions  of  water,  (2)  proper  temperature,  and  (3)  access 
germination,  of  oxygen.  Simple  experiments  are  easily  con- 
ducted to  establish  these  facts,  which  are  also,  in  part, 
matters  of  familiar  observation.  Thus  when  a  crop  of 
grain  has  been  sown  it  is  well  understood  that  it  will  not 
come  up  if  the  earth  is  too  dry,  and  that  it  is  more  likely 
to  decay  in  the  ground  than  to  germinate  if  it  is  too  wet, 

1  Cf.  Darwin,  Power  of  Movement  in  Plants,  pp.  94,  98  ;  Lubbock, 
Seedlings,  II,  p.  6. 


GROWTH    OF   PLANTS    FROM    THE    SEED.  27 

and  careful  experiments  go  to  show  that  seeds  sprout 
more  promptly  and  surely  with  a  less  amount  of  water 
than  is  commonly  supplied  in  artificial  cultures.  Too 
high  or  too  low  a  temperature  is  equally  unfavorable, 
although  there  is  a  pretty  wide  range  within  which  most 
seeds  will  germinate.  An  even  temperature  is  found  to 
be  more  favorable  to  prompt  germination  than  a  variable 
one.  Finally,  if  oxygen  is  excluded,  even  if  all  other  con- 
ditions are  fulfilled,  germination  fails  to  take  place.  It  is 
for  the  purpose  of  securing  an  abundant  supply  of  oxygen 
that  we  leave  the  sawdust  lying  up  loosely,  rather  than 
closely  packed,  about  the  seeds,  when  we  are  raising  seed- 
lings in  the  laboratory.  For  the  same  reason,  a  light, 
loose  soil  is  more  favorable  for  gardening  than  a  compact 
and  heavy  one.  These  conditions  are  well  known,  and 
are  taken  into  account  in  practical  operations,  although  a 
comparison  of  different  seeds  during  germination  estab- 
lishes the  equally  important  fact  that  both  individual  and 
specific  peculiarities  exist.  Some  seeds  require  more 
moisture  than  others,  and  the  degree  of  temperature  most 
suitable  for  germination  varies  with  different  species,  ^and 
so  on.  An  interesting  series  of  experiments  on  the  condi- 
tions of  germination  and  the  individual  peculiarities  just 
referred  to  has  been  carried  out  at  the  Cornell  University 
Experiment  Station.  For  an  account  of  these,  see  Science, 
XIV  (1889),  p.  88. 

Some  of  the  phenomena  connected  with  germination  are 
of  much  interest  and  are  easily  observed.  The  first  step 
consists  in  the  forcible  absorption  of  water,  Attendant  phe- 
manifested  by  the  great  increase  in  size  of  ger-  nomena. 
minating  seeds,  and  the  pressure  they  exert  if  an  attempt 
is  made  to  confine  them  in  a  closed  vessel.  Testing  with 
a  thermometer  shows  that  the  process  of  germination  is 


28  STUDY    OF    COMMON    PLANTS. 

accompanied  by  a  rise  of  temperature,  and  chemical  ex- 
amination indicates  absorption  of  oxygen  and  exhalation 
of  carbon  dioxide ;  in  other  words,  respiration  is  going  on. 
The  length  of  time  during  which  seeds  retain  their 
vitality  has  been  the  subject  of  much  discussion.  Stories, 
Duration  of  frequently  repeated,  of  the  growth  of  grain 
vitality.  many  centuries  old,  taken  from  Egyptian  tombs, 
and  of  raspberry  seeds  from  a  Roman  skeleton  in  England, 
etc.,  are  generally  discredited,  for  the  reason  that  sufficient 
proof  is  lacking.  On  the  other  hand,  a  series  of  experi- 
ments, conducted  for  a  long  period  by  a  committee  of 
the  British  Association  for  the  advancement  of  science, 
shows  that  some  seeds  have  certainly  retained  their  ca- 
pacity for  germination  from  twenty  to  forty  years,  and 
even  longer.1 

1  Report  of  British  Association,  1857,  Dublin  meeting. 


THE   ROOT.  29 


III.     THE   ROOT. 

MATERIAL  REQUIRED. 

Roots  of   Indian   corn   and  other  seedlings   used  in  the  preceding 

exercise. 
The  lower  parts  of  a  fully  grown  corn-stalk,  showing  the  supporting 

roots. 

Aerial  roots  of  English  ivy,  or  trumpet-creeper. 
Turnips  and  other  fleshy  roots  from  the  market. 
Slips   of   Verbena,    Tradescantia,    and   other   common   conservatory 

plants. 

I.   Examine  more  in  detail  the  roots  of  seedlings  already 
studied. 

1.  Taking  specimens  of  Indian  corn  of  different  ages, 

note 

a.  Where  the  secondary  roots  arise. 

b.  Whether  any  of  them  have  given  rise  to  roots  of  a 

higher  order. 

c.  How  they  compare  in  these  particulars  with  those 

of  wheat. 

2.  Compare  the  roots  of  the  sunflower,  bean,  and  pea 

with  reference  to  the  same  points. 

II.    Study  the  root-hairs  of  various  seedlings,  beginning 
with  some  that  are  growing  on  blotting  paper. 

1.  On  what  parts  of  the  roots  are  they  produced? 

2.  Remove,  with  a  pair  of  fine  forceps,  a  portion  of  a 

root  where  it  is  thickly  covered  with    root-hairs. 


30  STUDY    OF   COMMON    PLANTS. 

(The  roots  of  wheat  or  oat  seedlings  are  excellent 
for  this  .purpose.)  Mount  in  water,  taking  care 
not  to  injure  the  delicate  tissue  by  undue  press- 
ure. Examine  under  a  high  power  of  the  com- 
pound microscope. 

a.  Observe  the  structure  of  the  root-hairs. 

b.  Ascertain  how  they  are  connected  with  the  body 

of  the  root.     Draw. 

c.  Run  iodine  solution   under  the  cover  glass,  and 

watch  the  effect.     What  do  you- infer  as  to  the 
permeability   of   the   cell   membrane   and   the 
capacity  of  the  cell  contents  for  absorption  ? 
3.    Pull  up  a  specimen  that  has  grown  in  clean  sand. 
Shake  off  as  many  of   the  adherent   particles   as 
possible.     Examine  under  a  good  lens.     It  will  be 
seen  that  many  grains  of  sand  still  remain  attached. 
Ascertain  whether  this  is  due  in  any  way  to  the 
presence  of  root-hairs. 

III.  Cut  off  the  tips  of  some  of  the  fine  roots  of  wheat 
or   oats   grown   under   a   bell-jar.     Mount  in  water,  and 
examine  with  the  compound  microscope.     Select  a  good 
specimen,  and  draw  the  end  carefully  so  as  to  show  the 
root-cap. 

IV.  Determine  in  what   part  of   the   root  increase  in 
length  takes  place..     Use  for  this  purpose  roots  of  Indian 
corn,  peas,  or  sunflower,  growing  on  moist  blotting  paper 
under  a  bell-jar.     With  a  camel's-hair  brush  and  India  ink 
make  a  series  of  marks  at  intervals  of  a  millimeter,  begin- 
ning at  the  apex  of  the  root.     Replace  the  bell-jar,  and  as- 
certain by  subsequent   observations,  about   a   day  apart, 
where  elongation  has  taken  place. 

V.  Determine  the  direction  naturally  taken  by  roots. 


THE   ROOT.  31 

1.  Pull  up  beans  or  peas  that  have  been  growing  in  saw- 

dust, and  observe  the  entire  root  system.  How 
do  the  secondary  roots  compare  with  the  primary 
in  their  direction  of -growth?  If-  roots  of  a  higher 
order  have  been  formed,  ascertain  whether  they 
take  the  same  direction  as  either  of  the  preceding. 
Would  it  be  advantageous  for  the  plant  if  all  grew 
downward  ? 

2.  Take  a  germinating  pea  or  squash  seed,  with  a  radi- 

cle a  centimeter  or  more  in  length,  and  fasten  it 
to  a  cork  by  a  pin  so  that  the  radicle  will  point 
horizontally.  Keep  it  in  a  moist  atmosphere  under 
a  bell-jar,  and  exclude  the  light  by  covering  with 
a  dark  cloth.  Observe  the  subsequent  growth  of 
the  radicle.  Vary  the  experiment  by  turning 
other  specimens  so  that  the  radicle  will  point 
nearly  vertically. 

3.  Tie  a  piece  of  netting  over  the  mouth  of  a  beaker  or 

wide-mouthed  bottle  filled  with  water,  and  place  on 
it  a  number  of  seeds  of  white  mustard  that  have 
just  begun  to  germinate.  Allow  the  apparatus 
to  stand  in  front  of  a  window  without  being  dis- 
turbed, filling  with  water  occasionally,  so  that  the 
growth  of  the  seedlings  will  be  uninterrupted. 
Observe  the  direction  taken  by  the  roots. 

VI.    Examine   different   roots   with   reference    to   their 
mechanical  functions. 

1.  The  supporting  roots  of  Indian  corn.     Notice  where 

they  originate,  their  direction  of  growth,  and  their 
double  action  as  braces  and  guys. 

2.  Aerial  roots  of  the  English  ivy,  or  trumpet-creeper. 

Compare  these  with  ordinary  roots. 


32  STUDY  OF  COMMON  PLANTS. 

3.  Examine  under  a  lens  the  structure  of  a  blackberry 
root,  or  that  of  some  other  common  woody  plant. 
Cut  a  transverse  section,  and  notice  the  position 
of  the  wood  elements.  Compare  this  with  their 
arrangement  in  the  stem.  A  little  reflection  will 
show  that  the  arrangement  of  the  mechanical  ele- 
ments corresponds  with  the  very  different  condi- 
tions that  obtain  in  root  and  stem.  The  former 
must  be  so  constructed  as  to  resist  a  force  that 
tends  to  pull  it  out  of  the  ground ;  in  the  latter, 
on  the  other  hand,  resistance  to  a  lateral  and  ver- 
tical force  must  be  provided  for.1 
Other  roots  should  be  examined  in  the  same  way. 
Those  of  Indian  corn  seedlings  will  be  found 
useful. 

VII.  Compare  fully  grown  turnips  and  carrots,  radish, 
or  salsify  with  the  roots  of  seedlings  of  the  same  plants. 
What  changes  of  form  and  structure  have  they  undergone? 

VIII.  Study   the    formation   of   adventitious   roots,    as 
seen  in  Verbena  and  other  plants,  grown  by  florists  from 
slips.     Adventitious  roots  of  Tradescantia  can  be  obtained 
by  placing  a  fresh  branch  in  a  closed  bottle  so  that  the 
cut  end  will  stand  in  a  little  water  at  the  bottom. 

SPECIAL    STUDIES. 

I.  Protection  of  the  growing  point  of  the  root.  A 
number  of  water  plants  furnish  excellent  material 
for  microscopic  study  of  the  root-cap.  Among 
them  are  Lemna  minor,  common  everywhere  in 
stagnant  waters,  and  Pontederia  crassipes,  fre- 
quently grown  in  artificial  ponds.  Certain  aerial 

1  Cf.  Haberlanclt,  Physiologische  Pflanzenanatomie,  p.  125  ct  seq. 


THE  ROOT.  33 

roots,  as  those  of  Pandanus,  commonly  culti- 
vated in  conservatories,  also  have  remarkably 
developed  root-caps. 

II.  Conditions  affecting  the  formation  of  root-hairs. 
An  interesting  investigation  is  suggested  by 
Haberlandt,  Physiologisclie  Pflanzenanatomie,  p. 
147  et  seq. 

III.  Propagation  of  plants  by  slips  and  cuttings.     Ascer- 

tain what  plants  are  regularly  propagated  in  this 
way  by  florists  and  what  conditions  are  necessary. 

IV.  Reserve  materials  stored  in  roots.     Examination  of 

the  blackberry,  elecampane,  and  other  roots,  to 
determine  the  nature  of  the  food  substances  con- 
tained in  them. 

V.  Influence  of  moisture  on  the  direction  taken  by 
roots.  "  Search  for  water  "  by  roots  of  trees. 

VI.  Minute  anatomy  of  roots.  (This  may  be  deferred 
with  advantage  until  the  stem  is  studied  micro- 
scopically.) 

VII.  Estimate  of  the  total  length  of  the  root  system  of 
some  common  plants.  Johnson,  How  Crops 
Groiv,  p.  242. 

VIII.  Roots  of  parasites.  Sections  of  roots  of  Comandra 
or  mistletoe,  with  a  study  of  their  relation  to  the 
plants  on  which  they  have  fastened. 

REVIEW    AND    SUMMARY. 

Roots  function  as  organs  of  absorption,  as  storehouses  of 
reserve  materials,  and  as  a  mechanical  means  of  holding 
the  plant  firmly  in  its  place. 


34  STUDY  OF  COMMON  PLANTS. 

As  organs  of  absorption,  it  is  essential  that  they  should 
have  a  large  extent  of  surface  in  contact  with  the  soil. 
Eoots  as  ^n  PuHmg  UP  seedlings  of  different  sorts  it  is 
organs  of  apparent  that  the  total  length  of  their  roots 
is  many  times  that  of  the  aerial  parts,  and  this 
is  frequently  still  more  striking  when  the  earth  is  carefully 
washed  away  so  as  to  expose  the  whole  root  system  of 
older  plants.  The  surface  is  further  increased  by  the 
formation  of  root-hairs.  These  are  delicate,  elongated 
cells,  arising  from  the  roots  back  of  their  growing  point, 
and  so  numerous  under  favorable  conditions  as  to  give 
them  a  densely  hairy  appearance,  easily  noticeable  to  the 
unaided  eye.  By  their  adhesive  surface  the  root-hairs 
attach  themselves  closely  to  the  particles  of  soil,  and  by 
means  of  acid  excretions  aid  in  preparing  for  absorption 
the  crude  food  materials  of  the  earth.  These  substances, 
in  solution,  are  then  taken  up  and  carried  to  the  parts 
within.  It  is,  moreover,  through  the  agency  of  the  root- 
hairs  that  the  enormous  volume  of  water  evaporated  by 
the  leaves  of  plants  in  full  foliage  is  taken  up  from  the 
soil  and  started  on  its  upward  course.1 

The  roots  of  many  plants,  particularly  those  that  live 
more  than  a  year,  fulfil  an  important  function  as  reservoirs 
Eoots  as  °f  reserve  materials  upon  which  the  plant  draws 
storehouses,  when  it  begins  anew  its  period  of  active  growth. 
Suitable  tests  show  that  starch  and  sugar  are  the  food 
substances  most  commonly  stored  in  roots;  inulin  also 
occurs,  though  more  rarely.  These  and  other  vegetable 
products  are  described  in  detail  by  Sachs  in  his  Physiology 
of  Plants.  The  shape  taken  by  roots  that  serve  as  store- 
houses is  sometimes  quite  characteristic.  As  examples 

1  Johnson,  How  Crops  G-row,  p.  243 ;  Haberlandt,  Physiologische 
Pflanzenanatomie,  pp.  148,  149. 


THE   ROOT.  35 

may  be  mentioned,  the  napiform  roots  of  most  turnips,  the 
conical  roots  of  carrot,  salsify,  etc.,  the  moniliform  roots  of 
some  pelargoniums,  and  so  on. 

Besides  acting  as  organs  of  absorption  and  as  storehouses 
of  reserve  materials,  roots  fulfil  a-n  important  function  in 
holding  the  plant  firmly  in  its  place.  A  study  Mechanical 
of  the  arrangement  of  their  tissues  shows  a  functions, 
manifest  adaptation  to  this  function,  the  mechanical  ele- 
ments being  placed  compactly  at  the  center,  a  position  in 
which  they  are  able  to  resist  to  the  best  advantage  a 
pulling  force  that  tends  to  break  the  root  or  draw  it  out 
of  the  ground.  Such  aerial  roots  as  those  of  the  poison 
ivy  serve  to  hold  the  stem  securely  to  some  external  sup- 
port, and  the  prop  roots  of  Indian  corn  that  arise  a  little 
above  the  surface  of  the  ground  constitute  an  admirable 
system,  of  braces  and  guys,  by  which  the  stalk,  with  its 
heavy  load  of  ears,  is  enabled  to  maintain  an  erect  posi- 
tion. Considering  the  size  and  weight  attained  by  a 
single  cornstalk  with  its  fruit,  and  its  exposure  to  heavy 
winds  and  rain,  it  is  difficult  to  conceive  of  a  more 
effective  and,  at  the  same  time,  more  simple  mechanical 
arrangement. 

In  their  mode   of   growth  roots  exhibit   a   remarkable 
adaptation  to  their  environment.     Growth  in  length  takes 
place  just  behind  the  tip,  which  is  thus  free  to        Mo(Je  of 
turn  in  any  direction,  curving  aside  as  it  meets        growth, 
obstacles,  and  directing  its  way  towards  moisture  or  food, 
as  occasion  requires,  without  involving  any  disturbance  of 
the  older  parts  that  have  already  become  fixed  in  the  soil. 
The  growing  point  is  covered  by  the  root-cap,  and  thus 
protected  from  injury. 

The    primary   root   grows   perpendicularly  downwards, 
but  the  secondary  roots,  reacting  differently  to  the  pull  of 


36  STUDY   OF   COMMON   PLANTS. 

gravitation,  grow  down  obliquely,  while  roots  of  a  higher 

order   extend    indifferently  in  various    directions.      The 

result  is  such  a  distribution  of  the  root  system 

Primary  and  '  .         .     .  „  • 

secondary  as  to  bring  it  into  contact  with  the  soil  far  more 
roots,  perfectly  than  if  the  roots  grew  down  together 

in  a  common  bundle.  It  has  been  noticed,  however,  that  if 
the  end  of  the  primary  root  is  destroyed  one  or  more  of  the 
secondary  roots  near  it  grow  vertically  downward  to  take 
its  place.1 

While  the  branches  arising  from  the  first  or  primary 
root  are  properly  called  secondary,  the  same  term  is  also 
Adventitious  frequently  applied  to  roots  of  a  higher  order, 
roots,  and  is  sometimes  rather  loosely  extended  to 

those  given  off  by  the  stem  and  other  parts  of  the  plant. 
The  latter,  however,  are  commonly  spoken  of  as  adventi- 
tious. Aerial  roots,  such  as  those  of  the  ivy  and  trumpet- 
creeper,  properly  fall  under  this  head.  Other  adventitious 
roots  are  of  great  importance  in  the  practical  operations 
of  florists  and  gardeners,  enabling  them  to  increase  their 
stock  by  taking  advantage  of  the  capacity  of  slips  and 
cuttings  for  promptly  forming  roots.  The  readiness  with 
which  cuttings  of  willows  and  poplars  produce  adventitious 
roots,  together  with  their  rapid  growth,  has  led  to  their 
extensive  planting  in  the  western  states,  and  many  trouble- 
some weeds  owe  their  pertinacious  hold  on  the  soil  to  the 
same  habit. 

In  a  comparatively  small  number  of  plants,  of  which  the 
dodder  is  a  familiar  example,  adventitious  roots  take  the 
Parasitic  form  of  suckers  which  penetrate  the  tissues  of 
habits,  other  plants,  on  which  they  live  as  parasites. 

The  plant  thus  attacked  is  called  the  host,  from  the  rela- 
tion in  which  it  stands  to  its  parasite.  But  few  flowering 

1  Darwin,  Power  of  Movement  in  Plants,  p.  196. 


THE   ROOT.  37 

plants  have  become  truly  parasitic,  the  habit,  as  it  occurs 
in  the  vegetable  kingdom,  being  chiefly  characteristic  of 
fungi. 

In  their  microscopic  structure  roots  exhibit  essentially 
the  same  tissues  and  elements  as  are  found  in  the  stem, 
which  we  shall  soon  study  in  detail.  There  are,  Minute  anat. 
to  be  sure,  certain  differences  of  arrangement,  °my- 
already  mentioned  in  connection  with  the  mechanical  func- 
tion of  roots,  that  cannot  here  be  discussed  at  length. 
Those  who  wish  to  make  a  thorough  study  of  the  minute 
anatomy  of  roots  will  find  the  necessary  assistance  in  such 
works  as  Strasburger's  Practical  Botany  and  De  Bary's 
Comparative  Anatomy  of  the  Phanerogams  and  Ferns. 


38  STUDY  OF  COMMON  PLANTS. 


IV.     THE   STEM. 

MATERIAL  REQUIRED. 

Fresh  shoots  of  apple-tree,  grape-vine,  oak,  elder,  and  basswood. 
Stalks  of  Indian  corn  put  up  in  alcohol  after  they  have  attained  full 

size.     Stems  of  common  greenbrier,  Smilax  rotundifolia,  L. 
Shoots  of  white  pine  from  one  to  three  years  old,  preserved  in  alcohol. 

Similar  specimens  of  arbor  vitae  or  of  red  cedar. 
Specimens  of  white  oak,  hickory,  ash,  Norway  spruce,  palm,  and  other 

woods,  showing  transverse  and  longitudinal  sections. 
A  collection  of  greenhouse  plants,  including  rose  geranium,  primrose, 

Coleus,  Tradescantia,  and  others. 
Tendrils  of  grape-vine,  spines  of  honey  locust,  common  potato,  and 

such  other  modified  stems  as  are  procurable. 

STRUCTURE    AND    MODE    OF    GROWTH. 

I.    Study  first  the  gross  anatomy  of  a  number  of  woody 
stems. 

1.  With  a  sharp  knife  make  a  transverse  section  of  a 

one-year-old  shoot  of  an  apple-tree.  Examine 
under  a  good  lens,  and  draw  an  enlarged  outline, 
showing  the  position  and  relative  proportions  of 
pith,  wood,  and  bark. 

2.  Separate  the  bark  into  its  three  layers, 

a.  External,  corky  layer. 

b.  Middle,  green  layer,  not  sharply  delimited  from  the 

c.  Inner  bark,  or  bast. 

x          Try  the  strength  of   these  different   parts   by  sepa- 
rating and  pulling  upon  them. 


THE   STEM.  39 

3.  Examine   the  wood   closely.     Notice   the   medullary 

rays,  appearing  like  lines  radiating  from  the  pith. 
Careful  inspection  shows  numerous  openings  in 
the  wood  between  the  medullary  rays.  These  are 
the  ends  of  vessels  that  convey  water  and  air 
through  the  stem.  It  can  also  be  observed  that 
the  pith  is  made  up  of  minute  cells.  These  struct- 
ures may  be  seen  still  more  readily  in  the  grape- 
vine. 

4.  With  the  stem  of  the  apple-tree  compare  those  of  the 

grape-vine,  common  elder,  and  oak,  making  trans- 
verse sections,  as  before.  In  what  respects  do 
they  all  agree ?  How  do  they  differ? 

II.  Examine    the   stem   of   Indian   corn,   making   both 
transverse  and  longitudinal  sections.     What  part  of  the 
stem  has  the  firmest  tissue  ? 

Make  an  outline  sketch  of  the  transverse  section,  show- 
ing the  position  of  the  woody  parts  as  they  appear  under 
a  good  lens.  Compare  with  this  a  similar  section  of  the 
stem  of  a  palm  or  other  monocotyledonous  plant.  Com- 
mon greenbrier  is  suitable  for  this  purpose. 

III.  Study  shoots  of  white  pine,  two  or  three  years  old, 
that  have  lain  some  time  in  alcohol.     Indicate  by  means 
of  a  diagram  the  relative  position  of  pith,  wood,  and  bark. 

Using  $n  older,  dry  specimen,  that  has  been  cut  so  as 
to  show  a  smooth  transverse  section,  notice  the  succession 
of  annual  rings.  How  does  the  outer  edge  of  each  ring 
differ  from  the  inner?  Determine  the  age  by  counting 
the  number  of  rings.  Examine  the  stem  of  the  arbor 
vitae  or  red  cedar,  and  see  if  it  corresponds  in  structure 
with  that  of  the  white  pine. 

IV.  Write  an  account  of  the  different  stems  you  have 


40  STUDY    OF   COMMON    PLANTS. 

studied.  Show  how  the  stem  of  a  monocotyledon,  such  as 
Indian  corn,  differs  from  that  of  the  apple-tree  and  other 
dicotyledonous  plants.  With  which  do  the  stems  of  the 
conifers  (pine,  arbor  vitse,  etc.)  agree  ? 

V.  Ascertain  the  age  of  specimens  of  white  oak,  hickory, 
ash,  pine,  and  Norway  spruce,  by  counting  the  annual 
rings.  The  work  must  be  done  with  care,  in  order  to 
insure  accuracy.  In  examining  large  sections,  draw  a 
straight  line  from  the  center  to  the  periphery,  and  mark 
off  on  it  intervals  of  exactly  one  inch,  beginning  on  the 
outside.  Count  the  number  of  rings  in  each  division  and 
record  them  in  their  order.  Compare  the  rapidity  of 
growth  of  the  pine  and  spruce ;  of  the  ash  and  hickory.1 

MINUTE    ANATOMY. 

I.  Take  fresh  shoots  of  the  apple-tree,  and  cut  a  number 
of  transverse  sections.  Mount  some  in  water,  others  in 
glycerine,  and  still  others  in  Schulze's  solution  for  micro- 
scopic study.2  Examine  first  with  the  low  power.  Tak- 
ing the  parts  in  order,  beginning  with  the  outside,  we  find 

1.  The  outer  bark,  or  cork,  consisting  of  several  layers 

of  flattened  cells  with  reddish-brown  contents. 
(The  remains  of  the  epidermis  outside  of  the  cork 
may  be  disregarded.) 

2.  The  middle  bark,  or  cortical  parenchyma,  consisting  of 

a  broad  zone  of  cells  with  green  contents  (chloro- 
phyll). Near  the  inner  edge  of  this  zone  are 
bundles  of  thick-walled  elements,  bast  fibers.  The 

1  Other  species  may  of  course  be  used  if  more  convenient. 

2  The  success  of  the  work  depends  upon,  having  good  sections  to  study. 
Worthless  ones  must  be  thrown  away,  and  sectioning  continued  unt» 
entirely  satisfactory  specimens  are  obtained. 


THE   STEM.  41 

latter  are  nearly  colorless,  their  very  small  cavity 
showing  as  a  dark  point  at  the  center. 

3.  The  inner  bark.     This  is  best  studied  in  stems  four 

or  five  years  old.     It  is  composed  of 

a.  Sieve-tubes,    narrow   elements    with    light-colored 

walls. 

b.  Bast  parenchyma,  much  wider  cells  frequently  con- 

taining chlorophyll. 

c.  Bundles  of   bast   fibers   similar   to   those    already 

described. 

4.  Cambium.     In  the  winter  a  sharp  line  of  demarcation 

between  wood  and  bark  is  seen,  but  in  spring  there 
is  formed  a  zone  of  fresh  tissue  known  as  the  cam- 
bium, from  the  inner  cells  of  which  a  new  layer  of 
wood  is  produced,  and  from  the  outer  ones  a  new 
•  layer  of  bark.  See  VII  below. 

5.  The  wood.     In  this  observe  the  following: 

a.  Vessels  with  large  openings. 

b.  Wood  fibers,  smaller  elements  with  narrow  lumen 

and  thick  wall. 

c.  Wood  parenchyma,     This  is  more  easily  made  out 

on  longitudinal  section. 

d.  Medullary  rays,  extending  from  the  pith  outwards 

and  continuous  with  those  of  the  inner  bark. 

6.  Pith,  consisting  of  very  large  cells  marked  by  numer- 

ous pits. 

II.  Prepare  next  a  number  of  radial  longitudinal  sec- 
tions, mounting  as  directed  above,  and  study  in  the  same 
order,  comparing  them,  step  by  step,  with  corresponding 
parts  of  the  transverse  sections. 

1.  Ascertain  whether  the  cork  cells  present  the  same 
appearance  on  transverse  and  longitudinal  sec- 


42  STUDY    OF   COMMON    PLANTS. 

tions,  and  in  the  same  way  compare  the  cells  of 
the  cortical  parenchyma  as  seen  in  both. 

2.  Taking   the   inner   bark    next,    the    sieve-tubes    are 

easily  recognized  by  their  narrowness  and  length, 
and  also  by  their  soft,  light-colored  walls,  while 
the  bast  parenchyma  consists  of  much  shorter  and 
wider  cells.  The  medullary  rays  present  a  marked 
appearance,  looking,  on  radial  sections,  like  brick 
work. 

3.  Look  for  crystals  of  calcic  oxalate,  often  found  in  con- 

siderable numbers  in  cells  adjacent  to  the  sieve- 
tubes. 

4.  The  bast  fibers  are  to  be  looked  for  in  places  corre- 

sponding to  their  position  in  the  transverse  section. 
They  may  or  may  not  be  found  in  some  of  the  lon- 
gitudinal sections.  Why  ? 

When  you  have  found  them,  note  the  points  in  which 
they  differ  from  all  the  other  elements  of  the  bark. 

5.  Passing  to  the  wood,  the  large  pitted  vessels  are  at 

once  recognized.  It  is  seen  that  they  are  com- 
posed of  long  cylindrical  cells  placed  end  to  end, 
their  dividing  walls  having  been  absorbed,  or  with 
only  traces  of  them  remaining,  so  that  they  form 
continuous  ducts.  The  wood  fibers  also  are 
greatly  elongated,  but  are  much  narrower.  Their 
walls  are  very  thick  and  the  ends  tapering,  fitting 
to  each  other  so  as  to  make  a  very  compact  and 
solid  tissue. 

Notice  whether  the  medullary  rays  present  the  same 
appearance  in  the  wood  as  in  the  bark.  Test  the 
contents  with  iodine  solution.  Cells  resembling 
those  of  the  medullary  rays,  but  extending  length- 
wise of  the  stem,  will  be  found.  These  constitute 
the  wood  parenchyma. 


THE   STEM.  43 

6.  The  pith  comes  last,  and  presents  no  difficulties. 

7.  Having  compared  the  two  sections  throughout,  go 

over  them  again  and  see  if  all  is  clearly  under- 
stood. Make  yourself  familiar  with  all  the  details 
of  structure.  Note  what  cells  contain  chlorophyll, 
where  starch  occurs,  the  action  of  Schulze's  solu- 
tion on  different  parts,  whether  the  sieve-tubes 
show  any  peculiarities  corresponding  to  their  name, 
how  the  cork  originates,  the  manifest  resistance  of 
the  cork  cells  to  reagents,  and  so  on.  Write  a  full 
account,  and  introduce  drawings  wherever  they  are 
required  to  make  the  description  clear. 

8.  Finally   cut   tangential    longitudinal    sections,   and 

compare  with  the  preceding. 

III.  Stem  of  Indian  corn.     Cut  thin  transverse  sections. 
Examine  first  with  the  low  and  afterwards  with  the  high 
power.     The  following  parts  are  seen : 

1.  The   epidermis  and  sub-epidermal   tissue,  forming  a 

continuous  peripheral  zone  of  thick-walled  cells. 

2.  Fibre-vascular  bundles,  more  numerous  near  the  out- 

side of  the  stem. 

3.  Fundamental  tissue,  consisting  of  large  cells  similar  to 

those  composing  the  pith  of  the  apple-tree  stem. 

IV.  To  understand  these  parts  it  will  be  necessary  to 
compare  them  /carefully  with  the  same  structures  as  seen 
in   longitudinal   section.     Accordingly,  with   both    trans- 
verse and  longitudinal  sections  on  the  slide,  study  each 
part  in  detail. 

1.  Observe   the   epidermis   from   both   points   of   view. 

Draw  a  few  cells. 

2.  The  fibro-vascular  bundles  present  a  somewhat  com- 

plicated structure.     They  are  bounded  externally 


44  STUDY   OF   COMMON   PLANTS. 

by  strong  bands  of  thick-walled  cells,  composing 
the  so-called  bundle-sheath,  which  may  be  continu- 
ous, or  thinned  out  on  the  sides  of  the  bundle. 

The  bundle  itself  presents  two  parts  for  study :  first, 
the  xylem,  or  wood,  which  includes  the  two  conspic- 
uous pitted  vessels  (recognized  by  their  very  large 
openings),  and  the  parts  immediately  adjacent ; 
and  second,  the  phloem,  or  bast  portion,  marked 
by  the  peculiar  appearance  of  its  elements  on 
transverse  section,  its  small  cells  being  fitted  in  at 
the  angles  between  larger  ones  in  such  a  way  as 
to  give  the  effect  of  mosaic  work.* 

Studying  first  the  xylem,  on  both  transverse  and 
longitudinal  sections,  we  find  that  it  consists  of 

a.  The   large   pitted   vessels   already   noticed.     Ex- 

amine their  structure  carefully,  observing  par- 
ticularly the  remains  of  the  partition  walls  in 
the  form  of  heavy  rings,  indicating  the  origin 
of  the  vessels  in  rows  of  cells  placed  end  to 
end.  One  or  more  smaller  vessels  lie  between 
them,  and  a  little  nearer  the  center  of  the 
stem.  One  of  these  is  conspicuously  marked 
by  heavy  thickenings  in  the  form  of  rings,  and 
is  called  an  annular  vessel.  Frequently  the 
surrounding  tissue  is  absorbed,  leaving  only 
the  rings  of  the  annular  vessel  to  mark  its 
place. 

b.  Thick-walled  elements  lying  between  the   large 

pitted  vessels. 

c.  Elements  with  thinner  walls  surrounding  the  an- 

nular vessel.  Some  of  these,  as  already  stated, 
have  disappeared,  leaving  an  irregular  open 
space. 


THE   STEM.  45 

The  two  sorts  of  elements  that  compose  the  phloem 
are  easily  recognized  on  both  transverse  and 
longitudinal  sections. 

a.  The  sieve-tubes  are  large,   with   nearly  or   quite 

transparent  contents,  and  here  and  there  a  per- 
forated transverse  septum  looking  like  a  sieve. 

b.  The  smaller  cells   placed   at   the    angles    of   the 

sieve-tabes   are  the   cambiform,  or  companion, 
cells.     Their  thicker  contents,  smaller  diame- 
ter, and  the  absence  of  sieve-plates  at  once  dis- 
tinguish them  from  the  preceding. 
Having   identified    all    the    parts    that    have    been 
named,  study  them  closely,  and  after  you  have 
become  perfectly  familiar  with  the  position  and 
structure  of  the  different  elements,  draw  and  de- 
scribe them.     Meantime,  look  for  any  additional 
features  to  which  your  attention  has  not  thus  far 
been  specially  directed.     See  if  you  can  recognize 
the  protophloem,  a  small  group  of  rather  indistinct 
cells  lying  between  the  phloem   and  the  bundle- 
sheath. 

Study,  too,  more  carefully,  the  structure  of  the  sieve- 
tubes.  Try  the  effect  of  picric  aniline  blue  on 
these  and  other  parts  of  the  bundle.  Apply 
Schulze's  solution  to  other  sections,  and  phloro- 
glucin  (followed  by  hydrochloric  acid)  to  still 
others,  and  note  the  results.  What  parts  of  the 
bundle  are  lignified?  How  about  other  parts  of 
the  stem  ? 

3.  The  fundamental  tissue.  Examine  the  large  cells 
composing  the  tissue,  using  both  transverse  and 
longitudinal  sections.  Ascertain  whether  the  large 
cells  of  which  it  is  made  up  present  the  same 


46  STUDY    OF   COMMON    PLANTS. 

appearance  and  structure  in  all  parts  of  the  stem. 
Test  the  contents  for  starch. 

V.  Having  become  acquainted  with  the  minute  anatomy 
of  the  stem,  study  it  from  a  mechanical  point  of  view, 
endeavoring  to  ascertain   whether   the   thick-walled   me- 
chanical elements  are  grouped  in  such  a  way  as  to  secure 
strength  with  economy  of  material.     Notice   the  disposi- 
tion of  the  heavy  sub-epidermal  tissue  in  a   continuous 
hollow  cylinder,  the  arrangement  of  the  fibro-vascular  bun- 
dles, and  the  way  in  which  the  elements  composing  the 
bundle-sheath  are  distributed.1 

VI.  Stem  of  white  pine.     The  structure  of  the  stem  of 
conifers  presents  various  interesting  peculiarities,  but  tho 
arrangement  of  the  parts  and  mode  of  growth  are  nearly 
identical  with  those  of  dicotyledonous  stems,  and,  moreover, 
have  been  so  fully  treated  in  a  number  of  laboratory  guides 
as  to  render  it  unnecessary  to  repeat  directions  for  their 
study.     The  student  is  recommended,  however,  to  carry 
out  substantially  the  same  plan  of  work  on  the  stem  of  the 
white  pine  as  is  outlined  in  the  section  on  the  Scotch  pine 
in  Arthur,  Barnes,  and  Coulter's  Plant  Dissection. 

VII.  Cambium.     Nearly  all  woody  species  in  temperate 
regions    of  the  globe    form   distinct   annual   rings   which 
mark  the  growth  of  the  wood  from  year  to  year.     In  order 
to  understand  the  process  a  study  of  the  cambium  should 
be  made.     Shoots  of  the  white  pine  four  or  five  years  old  are 
suitable  for  this  purpose.     They  should  be  cut  during  the 
season  of  active  growth,  say  from   June  to  August,  and 
placed  in  alcohol.     If  properly  hardened,  transverse  sec- 
tions may  be  obtained  that  show  very  perfectly  the  new 
wood  and  bark   formed  by  the    division    of   the    delicate 

1  Cf.  Strasburger,  Practical  Botany,  p.  88,  and  footnote. 


THE   STEM.  47 

cambium  cells.     Test  for  lignin,  and  study  the  mode  of 
development  of  the  wood.1 

PHYSIOLOGY   OF  THE   STEM. 
Protection. 

I.  Examine   under  a  lens   the   stem  of  the   cultivated 
verbena,  primrose,  and  other  plants  from  the  greenhouse. 

II.  Mount  portions  of  the  epidermis  of  each  in  water, 
and  examine  with  the  compound  microscope.     Draw  and 
describe  the  various  epidermal  appendages. 

III.  Make  a  careful  study  of  the  protective  arrange- 
ments of  the  common  thistle,  teasel,  honey  locust,  cactus, 
and  blackberry.      Ascertain  the  morphological  character 
of  their  various  protective  structures. 

IV.  Examine  various  woody  stems,  such  as  those  of  the 
hickory  and  oak.     Notice    ' 

1.  The  thickness  of  the  bark. 

2.  How  it  accommodates  itself   to  the  growth  of  the 

tree. 

V.  Enumerate  any  other  means  that  you  have  observed 
by  which  the  stems  of  plants  are  protected. 

Mechanical  Support. 

I.  Study  the  arrangement  of  the  wood  elements  of  the 
stem   of  the   common    elder.      Compare   it  with   a  stalk 
of   wheat ;    with    the    stem    of   a  palm.      Is  the  material 
economically  employed  ? 

II.  Make  a  transverse  section  of   the  stem  of  coleus. 
Examine  with  the  low  power  of  a  compound  microscope. 

1  In  connection  with  his  study  of  the  structure  of  stems,  the  student 
should  read  Gray's  Structural  Botany,  pp.  67-82. 


48  STUDY   OF   COMMON    PLANTS. 

Draw  an  outline  sketch,  locating  the  position  of  the  me- 
chanical elements. 

III.  Cut  through  an  old  tendril  of  a  grape-vine.     Notice 
the  disposition  of  the  wood  elements.     Test  its  strength. 

IV.  Study  under  the  compound    microscope  the  bast 
fibers  of  basswood  and  other  common  plants. 

V.  Write  a  brief  account  of  what  you  have  ascertained 
regarding  the  mechanical  arrangements  for  the  support  of 
the  plant.     Read  Goodale,  Physiological  Botany,  pp.  188- 
194 ;  Haberlandt,  Physiologische  Pflanzenanatomie,  p.  96 
et  seq. 

Transportation  of  Food  in  Solution. 

I.  Cut  a  short  branch  from  a  grape-vine.     Immerse  the 
cut  end  in  a  colored   solution,  such   as   red   ink.     After 
some  time  make  transverse  sections,  and  observe  how  far 
and  through  what  parts  of  the  stem  the  colored  fluid  has 
penetrated.1 

II.  Repeat  the  experiment,  using  a  fresh  leafy  stem  of 
Tradescantia   for   the    purpose.      Place    finely    powdered 
indigo  in  the  water  and  allow  the  plant  to  be  exposed  to 
sunlight.     This  time  take  the  precaution  to  cut  the  stem 
under  water  so  as  to  prevent  the  entrance  of  air.     If  the 
cut  is  made  slanting,  and  the  whole  operation  skillfully 
performed,  the  particles  of  indigo  can  be  seen  under  the 
compound   microscope  as  they  enter   the    vessels    of   the 
Tradescantia. 

Storage  of  Food. 

I.    Cut  a  common  potato  in  two.     Make  thin  sections 
from  the  exposed  surface,  and  examine  with  the  compound 

1  On  the  ascent  of  water  in  woody  plants,  see  H.  Marshall  Ward,  Tim- 
ber and  Some  of  its  Diseases,  Chap.  IV  (Nature  Series). 


THE   STEM.  49 

microscope.     Draw  one  or  two  cells  with  their  contents, 
taking  care  to  show  details  of  structure. 

II.  Examine  in   the   same   way  sections   from  various 
other  underground  stems,  such  as  ginger,  mandrake,  etc. 

III.  Prepare  sections  from  pieces  of  a  dahlia  "tuber"1 
that  have   lain    in   commercial    alcohol   for  some  weeks. 
Draw  a  few  cells,  showing  the  peculiar  sphere-crystals  of 
inulin. 

IV.  In  some  stems,  as,  for  example,  an  onion  bulb,  sugar 
is  stored.     This  may  be  tested  for  in  the  way  described  by 
Strasburger,  Practical  Botany,  p.  48. 

• 

MODIFIED    STEMS. 

I.  Make  a  thorough  study  of  the  common  potato,  ob- 
taining for  the   purpose  a  number  of  different  varieties. 
What  reasons  are  there  for  considering  it  a  stem  rather 
than  a  root?     What  are  the  "eyes"?     Where  are  they 
most  abundant?     Are   they  all  alike?      Find  where  the 
potato  was  attached.     Draw  an  outline  and  indicate  by 
a  dotted  line  the  direction  of  growth  in  length.     Does  it 
ever  branch?     Cut  a  transverse  section  so  that   it  will 
pass  through  a  bud.     Indicate  in  an  outline  sketch  the 
position  of  pith,  wood,  and  bark.     Notice  that  the  wood 
has  been  reduced  to  a  minimum.     It  appears  to  the  naked 
oye  as  a  faint  circular  line. 

Write  a   complete    description,  and    discuss    the    mor- 
phology of  the  potato.     See  Gray,  Structural  Botany,  p.  59. 

II.  Study  a  collection  of  other  modified  stems  in  the 
same  way,  endeavoring  in  each  case  to  satisfy  yourself  as 

1  This  is  really  a  root,  but  on  account  of  its  convenience  it  is  selected 
instead  of  a  stem. 


50  STUDY   OF    COMMON   PLANTS. 

to  every  morphological  feature.  The  following  and  a 
considerable  number  of  additional  species  can  usually  be 
obtained, — some  at  the  florist's,  others  at  the  grocery,  and 
still  others  at  the  drug  store  :  ginger,  iris,  geranium,  onion, 
crocus,  Solomon's  seal,  aconite,  calamus.  Fresh  indigenous 
plants  will  furnish  many  more. 

III.  Examine  specimens  of  as  many  of  the  following 
genera  as  are  procurable,  and  discuss  their  morphology: 
Muhlenbeckia,  Myrsiphyllum,  Ruscus,  Asparagus. 

In  such  exercises,  a  hasty  examination  of  external  feat- 
ures is  by  no  means  sufficient.  Every  species  taken  in 
hand  should  be  subjected  to  patient  and  thorough  study. 
Some  of  those  named  present  difficulties  that  are  not  likely 
to  be  overcome  by  a  student  who  is  unwilling  to  think. 


GROWTH    OF    STEMS    FROM    BUDS. 

I.  Obtain,  before    they   have  opened   in  spring,   well- 
developed  buds  of  lilac,  maple,  hickory,  horse-chestnut, 
Austrian   pine,  and   other   trees.     Study   them    carefully 
with  regard  to  protective    arrangements,  taking  account 
of  the  structure  and   position  of   the   bud-scales   (imbri- 
cated  like  the   shingles  of  a  roof),  waterproofing,  hairs ; 
in  short,  whatever  appears  to  contribute  to  the   protec- 
tion of  the  parts  within.     What  part  of  the  bud  is  best 
protected  ? 

II.  Study  next  the  arrangement  of  the  parts  composing 
the  bud,  taking  first  the  buds  of  the  lilac,  and  following 
with  those  of  the  horse-chestnut  and  other  trees.     Remove 
the  bud-scales  and  undeveloped  leaves  in  succession,  and 
lay  them  in  radiating  rows,  following  the  order  in  which 
they  are  placed  in  the  bud. 


THE   STEM.  51 

Is  the  arrangement  of  the  parts  of  the  bud  advantageous 
as  regards  economy  of  space  ?  Does  it  present  any  other 
advantages? 

Compare  the  last  year's  growth  of  the  stem  with  the  ter- 
minal bud,  bearing  in  mind  that  "  a  bud  is  an  undeveloped 
branch." 

III.  Examine  all  the  marks  on  a  horse-chestnut  branch. 
Three  kinds  of  scars  are  to  be  seen  ;  namely,  those  left  by 
the  foliage  leaves,  by  bud-scales,  and  by  flower-clusters. 
Compare  all  these  with  each  other  and  with  what  is  seen 
in  the  terminal  bud,  until  you  are  thoroughly  familiar  with 
the  characters  of  the  branch  as  they  appear  in  the  bud. 
Carry  out  a  similar  study  with  the  buds  and  branches  of 
other  trees.1 

IV.  Place  the  cut  ends  of  shoots  of  lilac,  horse-chestnut, 
apple,  etc.,  in  water,  the  latter  part  of  winter ;  keep  them 
in  a  warm  room,  changing  the  water  frequently,  and  ob- 
serve the  unfolding  of  the  buds.     Notice  the  first  observa- 
ble changes  as  well  as  those  occurring  in  later  stages. 
Record  your  observations  in  detail. 

V.  Compare  the  terminal  buds  of  plants  belonging  to 
different  genera,  e.g.  Acer,  Caiya,  and  Pinus,  and  deter- 
mine  whether   each   presents    distinctive   marks.      Next, 
compare  the  buds  of  the  red,  and  sugar  maple,  noting 
carefully  all  the  differences.     In  the  same  way,  compare 
the  buds  of  Austrian,  Scotch,  and  white  pine,  of  the  black 
walnut  and  butternut. 

As  opportunity  offers,  practice  the  identification  of  trees 
in  winter  by  means  of  buds  and  other  parts.2 

1  For  an  admirable  study  of  the  buds  and  branches  of  common  trees, 
see  Newell,  Outlines  of  Lessons  in  Botany,  Part  I.     Ginn  &  Co. 
2Cf.Poerste,  Bot.  Gaz.,  XVII  (1892),  p.  180. 


52  STUDY   OF   COMMON    PLANTS. 


REVIEW    AND    SUMMARY. 

The  stems  of  plants  exhibit  certain  inherited  pecu- 
liarities of  form,  structure,  and  habit.  In  some  large 
Fwm  families,  the  mints,  for  example,  the  stem  is 

structure,  square ;  while  in  others,  as  the  true  sedges,  it 
is  triangular.  The  cylindrical  form,  however, 
which  has  important  mechanical  advantages  in  its  favor, 
is  most  common.  Characteristic  habits,  manifested  in 
mode  of  growth  or  choice  of  surroundings,  are  also  fre- 
quently met  with.  Thus,  the  family  to  which  the  morn- 
ing-glory belongs  is  particularly  distinguished  by  its 
climbing  habit,  the  members  of  the  water-lily  family  by 
their  aquatic  habits,  and  so  on.  Structural  peculiarities 
are  still  more  distinctive  and  far-reaching ;  so  that,  as  a 
rule,  we  readily  determine  the  class  to  which  a  plant 
belongs  by  ascertaining  the  arrangement  of  the  tissues 
composing  the  stem. 

The  texture  of  the  stem,  as  determined  by  the  nature 
of  its  elements,  is  often  characteristic.  Various  families 
Texture  and  °^  plants,  as  those  to  which  the  maple,  oak, 
duration,  and  willow  belong,  have  woody  stems ;  while 
others,  as  the  pink  and  violet  families  and  many  others, 
are  herbaceous.  The  duration  of  the  plant  corresponds 
rather  closely  to  the  nature  of  the  stem.  Woody  plants 
are  perennial,  living  for  an  indefinite  period,  while  herba- 
ceous ones  are  commonly  annual  or  biennial.  These  dis- 
tinctions, however,  are  not  to  be  pressed  too  far,  since  the 
texture  of  the  stem  is  subject  to  much  variation,  even  in 
the  same  species,  and  duration  is  greatly  influenced  by 
climatic  conditions. 

While  typical  stems  are  distinguished  by  the  various 
characters  already  referred  to,  there  are  many  others  that 


THE   STEM.  53 

have  taken  modified  forms  corresponding  to  special  func- 
tions that  they  have  assumed.  Thus  many  stems,  Modified  or 
a  large  proportion  of  which  are  subterranean,  derived  forms, 
serve  chiefly  as  reservoirs  of  reserve  materials,  and  in  the 
course  of  time  have  undergone  striking  modifications  both 
of  form  and  structure.  The  tuber  of  the  common  potato 
shows  all  the  essential  characters  of  a  dicotyledonous  stem 
in  the  formation  of  buds,  the  concentric  arrangement  of 
pith,  wood,  and  bark,  and  in  still  other  respects,  but  the 
fibrous  tissue  has  almost  wholly  disappeared,  while  the 
cellular  tissue  has  increased  to  such  an  extent  as  to  give 
the  tuber  the  appearance  of  a  monstrosity  compared  with 
the  ordinary  branches  of  the  same  plant.  Quite  as  strik- 
ing changes  are  seen  in  branches  that  have  taken  the  form 
of  spines  and  assumed  the  function  of  protection.  Good 
examples  of  these  are  the  spines  of  the  hawthorn  and 
other  familiar  plants.  Even  more  remarkable  modifica- 
tions are  presented  in  the  leaf-like  organs  known  as 
cladophylls.  In  the  case  of  the  so-called  smilax  of  the 
greenhouses,  the  true  leaves  are  inconspicuous  scales, 
while  the  cladophylls  so  perfectly  simulate  foliage  leaves 
as  to  deceive  an  inexperienced  eye.  Much  caution  is 
necessary  in  studying  the  morphology  of  these  and  other 
modified  branches.  Their  position  on  the  stem,  structure, 
and  mode  of  growth,  and  any  tendency  they  may  exhibit 
to  become  ordinary  leaf-bearing  shoots,  are  all  to  be  taken 
into  account. 

In  their  anatomical  structure  and  mode  of  growth,  stems 
present  well  marked  peculiarities,  which,  as  already  stated, 
are  sufficiently  characteristic  to  admit  of  the  Anatomical 
ready  determination  of  the  great  class  to  which  ^™^e  and 
a  plant  belongs.     The  stems  of  a  large  propor-  growth, 
tion  of  monocotyledons  are  well  represented  by  that  of 


54  STUDY   OF   COMMON   PLANTS. 

Indian  corn.  In  this  the  fibro -vascular  bundles  are  scat- 
tered through  the  fundamental  tissue  so  that  there  is  no 
Monocotyle-  manifest  distinction  of  pith,  wood,  and  bark,  and 
dons,  both  here  and  in  other  members  of  the  same 

class  certain  mechanical  arrangements  of  much  interest 
present  themselves.  In  the  stem  of  Indian  corn  a  strong 
cylindrical  band  of  sclerenchyma  is  placed  just  beneath 
the  epidermis,  a  disposition  of  the  mechanical  elements 
adapted  to  secure  the  greatest  strength  with  the  least 
amount  of  material ;  and  the  same  principle  is  carried  out 
in  the  bundles  themselves,  the  sheaths  of  which  are  much 
thickened  radially,  thus  aiding  materially  in  preventing 
bending  of  the  stem,  and  also  protecting  the  vessels  and 
other  conducting  elements. 

The  stem  of  dicotyledons  presents  a  rather  more  com- 
plicated structure.  As  seen  in  the  apple  shoot,  which 
may  be  taken  as  a  representative,  the  pith, 
wood,  and  bark  are  arranged  concentrically. 
In  the  bark,  as  a  rule,  three  layers  may  be  distinguished, 
viz.,  outer  bark  or  cork,  middle  bark  or  green  layer,  con- 
sisting chiefly  of  large  cells  containing  chlorophyll  and 
other  materials,  and  inner  bark  or  bast,  characterized  by 
the  presence  of  sieve-tubes,  usually  with  bast  libers  and 
some  parenchyma.  Between  the  inner  bark  and  wood  is 
the  cambium  zone,  which  during  the  growing  season  is  a 
layer  of  delicate  cells,  by  the  multiplication  of  which  new 
wood  and  bark  are  produced.  The  Avood  consists  of  the 
large  vessels,  the  openings  of  which  are  conspicuous  on 
transverse  section,  wood  fibers  which  constitute  the 
greater  part  of  its  substance  and  give  the  wood  its 
rigidity,  and  the  medullary  rays,  to  which  in  many  species 
are  added  the  wood-parenchyma  cells.  The  pith  consists 
of  large  cells  which  commonly  present  no  distinctive 


THE   STEM.  55 

peculiarities.  Since  each  year,  in  temperate  regions,  the 
sterns  of  dicotyledons  add  a  new  zone  of  wood,  it  is 
possible  to  determine  the  age  of  a  tree  by  counting  the 
number  of  annual  rings.  Not  infrequently  the  record 
is  obscured  by  irregular  growth,  due  to  drought  and 
other  causes,  but  in  general  these  rings  are  clearly  defined. 

In  their  mode  of  growth  the  stems  of  gymnosperms 
agree  with  those  of  dicotyledons,  but  their  wood  elements 
are  peculiar,  the  wood  being  composed  mainly 
of  elongated  cells  called  tracheids,  the  radial 
sides  of  which  have  numerous  bordered  pits,  by  means 
of  which  they  communicate  with  each  other  and  with  the 
medullary  rays. 

The  structure  of  stems  corresponds  with  a  number  of 
very  important  .functions  performed  by  the  elements  that 
compose  them.  Thus  the  epidermis,  afterwards 
replaced  by  cork,  is  protective,  as  is  also  the 
bark,  which  on  the  trunks  of  most  trees  becomes  greatly 
thickened  with  advancing  age.  The  medullary  rays  and 
other  parenchyma  cells  of  wood  and  bark  serve  for  storage 
of  various  food  products,  and  are  also  employed  to  a  consid- 
erable extent  in  conducting  them  from  one  part  of  the  plant 
to  another.  Bast  and  wood  fibers  serve  a  special  purpose 
as  mechanical  elements  by  which  the  stem  is  maintained 
in  its  position,  and  enabled  to  resist  forces  that  tend  to 
strain  or  fracture  it.  Finally  the  vessels  and  tracheids  are 
chiefly  concerned  in  conducting  water  containing  mineral 
substances  and  air  from  the  roots  to  the  upper  parts  of  the 
plant,  while  the  sieve-tubes  of  the  inner  bark  store  up 
nitrogeneous  food  materials,  and  convey  them  to  the  points 
where  they  are  needed. 

It   will,    of   course,    be   understood    that   an   adequate 
account  of   the   physiology  of   stems  cannot  possibly  be 


56  STUDY   OF   COMMON    PLANTS. 

condensed  into  such  a  summary  statement  as  the  fore- 
going ;  but  it  will  at  least  serve  to  point  out  the  important 
parts  played  by  the  various  elements  of  the  stem  as  they 
contribute,  each  its  share,  to  the  work  of  the  whole.  The 
mechanical  system  is  treated  at  length  by  Haberlandt, 
Physiologische  Pflanzenanatomie,  pp.  96—143,  and  an  ex- 
tended review  of  the  theories  regarding  the  ascent  of 
water  in  the  trunks  of  tall  trees  is  given  by  H.  Marshall 
Ward,  Timber  and  Some  of  its  Diseases,  Chap.  IV. 


THE   LEAF.  57 


V.     THE   LEAF. 

MATERIAL   KEQUIEED. 

Leaves  of  as  many  kinds  as  are  procurable.  See  suggestions  under 
"Systematic  Description."  Branches  of  basswood,  elm,  maple, 
and  horse-chestnut.  Leafy  plants  of  primrose,  fuchsia,  dandelion, 
and  geranium. 

Leaves  of  hyacinth  and  English  ivy. 

Leaves  of  various  hairy  plants  and  of  conifers,  rushes  and  sedges,  etc. 

Leaves  of  different  ferns  and  flowering  plants  called  for  under  "Me- 
chanical and  Conducting  System." 

Specimens  of  Elodea  Canadensis  growing  in  water,  and  of  Mnium  or 
other  common  moss. 

Tropaeolum  and  other  convenient  plants  growing  in  pots 

A  collection  of  modified  leaves. 

SYSTEMATIC    DESCRIPTION. 

Write  a  careful  and  complete  description  of  the  leaves 
of  ten  or  a  dozen  different  plants,  following,  as  far  as  it 
proves  serviceable,  the  schedule  given  below. 

Some  one  has  said  that  "  there  is  no  part  of  botany  so 
overwhelmed  with  cumbrous  terminology  as  that  which 
relates  to  leaves."  Nevertheless  the  really  necessary 
terms  are  easily  learned,  and  the  peculiarities  expressed 
by  them  are  far  from  accidental.  The  form  of  the  leaf,  its 
position  on  the  stem,  the  venation  and  other  structural 
features  are  generally  such  as  to  secure  the  greatest  effi- 
ciency, and  in  studying  these  it  is  desirable  to  be  able 
to  express  one's  self  with  exactness.  The  greenhouse  or 


58  STUDY    OF   COMMON   PLANTS. 

window  garden,  the  drug  store,  collections  of  preceding 
years,  and  seedlings  raised  in  the  laboratory  will,  even  in 
winter,  furnish  abundant  material.  The  following  may  be 
suggested  as  a  partial  list :  English  ivy,  geranium,  prim- 
rose, verbena,  rose,  oxalis,  maurandia,  nasturtium,  oak, 
maple,  elm,  lily,  Indian  corn,  hyacinth,  amaryllis,  arbor 
vitse,  hemlock,  juniper,  and  different  species  of  pines. 

Schedule  for  Leaf  Description. 

1.  Position.     Radical 2  or  cauline. 

2.  Arrangement.     Opposite,  alternate,  whorled,  fascicu- 

late. 

3.  Relation    to    Stem.       Petiolate,    sessile,    perfoliate, 

sheathing,  connate,  decurrent,  etc. 

4.  Stipules.     Described  as  leaves.     If  absent,  the  leaf  is 

said  to  be  exstipulate. 

5.  Form.     Acicular,  awl-shaped,  linear,  oblong,  ellipti- 

cal,   oval,    rotund,    ovate,    lanceolate,    reniform, 
obovate,  oblanceolate,  etc. 

6.  Apex  and  Base.    For  special  terms  see  dictionary  and 

text-books. 

7.  Margin.      Entire,  serrate,  dentate,  crenate,  sinuate, 

irregular,  lobed,  cleft,  parted,  divided,  etc. 

8.  Venation.     Pinnate,  palmate,  parallel. 

9.  Surface.     Glabrous,  glaucous,  pubescent,  wooly,  vil- 

lose,  hirsute,  prickly,  etc.    (These  terms  apply  also 
to  the  surface  of  other  organs.) 

10.  Compound  Leaves.  Pinnate,  bi-pinnate,  tri-pinnate, 
palmate,  bi-palmate,  tri-palmate,  pinnately  or  pal- 
mately  decompound,  etc. 

1  Gray's  Lessons,  Section  7,  and  illustrations  of  botanical  terms  in 
Webster's  International  Dictionary  should  be  consulted. 

2  A  misleading  term,  but  fixed  in  the  language. 


THE   LEAF.  59 


LEAF    ARRANGEMENT. 

I.  Take  branches  of  basswood,  elm,  maple,  and  horse- 
chestnut,  and  study  the  leaf  arrangement.     In  winter  the 
position  of  the   leaves  of  preceding   years  may  be  deter- 
mined by  the  leaf -scars. 

Are  the  leaves  placed  advantageously  as  regards  expos- 
ure to  light  ?  Cf .-  Lubbock,  Flowers,  Fruits,  and  Leaves, 
pp.  103-114. 

II.  Compare   other   plants,   e.g.   primrose    and   fuchsia, 
dandelion  and  geranium,  with  regard  to  this  principle. 

III.  Try  the  effect  of  putting  the  leaves  of  one  species 
on  the    branches    of   another,  without  changing  the  leaf 
arrangement. 

MINUTE   ANATOMY. 

I.  With  a  pair  of  fine  forceps  strip  off  a  portion  of  the 
epidermis  of  a  hyacinth  leaf.  Mount  in  water  and  examine 
under  the  high  power  of  a  compound  microscope.  Observe 

1.  The  elongated  epidermal  cells  destitute  of  chlorophyll. 

2.  The  stomata,  each  with  two  reniform  guard-cells  con- 

taining chlorophyll  bodies.     Draw. 

II.  Place  a  small  portion  of  a  leaf  of  the  English  ivy 
between  two  pieces  of  pith,  and,  with  a  keen  razor,  cut  a 
number  of  transverse  sections.  Examine  under  the  com- 
pound microscope.  Select  a  section  that  shows  all  the 
structural  details  and  draw  accurately.  Beginning  with 
the  upper  surface  the  section  shows 

1.    The  upper  epidermis,  consisting  of  a  single  layer  of 
thick-walled  cells,  destitute  of  chlorophyll. 


60  STUDY    OF    COMMON   PLANTS. 

2.  A  layer  or  two  of  closely  packed  cells,  with  their 

long  diameter  perpendicular  to  the  surface  of  the 
leaf,  containing  many  chlorophyll  bodies.  These 
constitute  the  palisade  tissue. 

3.  Other  chlorophyll-bearing  cells  essentially  the  same  as 

the  preceding,  but  less  regular  in  shape  and  more 
loosely  arranged,  so  that  toward  the  lower  surface 
of  the  leaf  large  openings,  intercellular  passages, 
occur.  Some  of  these  cells  contain  large  stellate 
crystals  of  oxalate  of  lime. 

4.  About  midway  between  the  upper  and  lower  surface, 

the  veins,  fibre-vascular  bundles,  cut  either  trans- 
versely or  at  an  angle,  according  to  their  direction 
at  the  place  where  the  section  is  made.  The 
thick-walled  mechanical  elements  constitute  the 
bundle-sheath.  The  bundle  itself  is  divided  into 
two  adjacent  parts,  the  xylem  lying  towards  the 
upper  surface  of  the  leaf,  and  the  phloem  towards 
its  lower  surface.  The  tracheids  of  the  xylem, 
elongated  tube-like  structures,  are  easily  recog- 
nized. 

5.  The  lower  epidermis,  similar  to  the  upper,  but  with 

stomata  at  frequent  intervals.  These  are  placed 
so  that  each  one  forms  an  entrance  to  one  of  the 
intercellular  passages.  (Sections  of  the  stomata 
are  best  studied  in  a  hyacinth  leaf.) 

NOTE.  —  The  different  sections  should  be  studied  until  the  gen- 
eral structure  of  the  leaf  is  thoroughly  understood.  Every  fact  is 
of  physiological  significance,  and  it  is  of  the  utmost  importance 
that  the  student  should  have  a  complete  and  clear  knowledge  of 
the  minute  anatomy  based  on  direct  observation. 


THE   LEAF.  61 

PHYSIOLOGY    OP   LEAVES. 
Protection. 

Leaves  require  protection  against 

1.  Changes  of  temperature. 

2.  Drying. 

3.  Attacks  of  animals,  fungi,  etc. 

4.  Injury  by  wind  and  other  meteorological  agencies. 

Cf.  Lubbock,  Flowers,  Fruits,  and  Leaves,  Chap. 
VI ;  Kerner,  Flowers  and  their  Unbidden  Guests. 

Some  of  the  following  observations  are  to  be  carried  out 
in  the  laboratory,  while  others  are  best  conducted  out  of 
doors. 

I.  Remove  the  epidermis  from  a  portion  of  a  hyacinth 
leaf,  or  the  leaf  of  some  other  fleshy  plant.     Notice  its 
texture,  strength,   and  elasticity.     After  a  time   observe 
any  changes  that  have  taken  place  in  the  part  from  which 
the  epidermis  has  been  removed. 

II.  Examine  the  hairy  covering  of  leaves  of  common 
mullein.     Compare   other  hairy  plants.     Examine   micro- 
scopically the  hairs  of  mullein,  verbena,  rose  geranium,  and 
other  common  species.     Make  a  series  of  drawings  illus- 
trating the  epidermal  appendages  of  various  leaves. 

III.  Study  the  leaves  of  the   Austrian  pine,  common 
juniper,  and  other   conifers.     Enumerate    the    protective 
arrangements  exhibited  by  them. 

IV.  Compare  very  young  leaves  of  the  oak,  apple,  or 
other  common  tree,  with  older  ones. 

V.  Many  plants  are  protected  by  disagreeable  or  poi- 
sonous substances  stored  in  their  foliage.     Name  any  of 
these  that  you  know. 


62  STUDY   OF   COMMON    PLANTS. 

VI.  Some    leaves    exhibit    remarkable    "sleep    move- 
ments."   What  are  these  for?    Cf.  Darwin,  Power  of  Move- 
ment in  Plants,  Chap.  VII. 

VII.  Other  leaves  exhibit  equally  remarkable  "hot  sun 
positions."   Of  what  use  are  these  to  the  plant  ?   Cf.  Wilson, 
Contributions  from  the  Bot.  Lab.  Univ.  of  Pa.,  Vol.  I,  No.  1. 

Mechanical  and  Conducting  System. 

The  skeleton  or  framework  of  the  leaf  serves  to  support 
the  delicate  green  tissue,  holding  it  so  as  to  expose  the 
largest  possible  surface  to  the  sun,  and,  at  the  same  time, 
giving  the  whole  structure  sufficient  rigidity,  strength,  and 
elasticity  to  resist  mechanical  violence.  It  also  serves  to 
conduct  a  constant  supply  of  water  and  mineral  substances 
to  every  part  of  the  leaf,  and  to  convey  away  elaborated 
food  materials.  It  is  only  by  keeping  these  principles  in 
mind  that  an  intelligent  study  of  venation  can  be  made. 
Cf.  Sachs,  Physiology  of  Plants,  pp.  48-53. 

I.  Obtain  the  leaves  of  several  ferns,  e.g.  Adiantum  pe- 
datum,  Aspidium  cristatum,  Osmunda  Claytoniana.     Draw 
an  enlarged  outline  of  a  leaflet  of  one  or  more  species, 
showing  the  exact  position  of  the  veins. 

II.  Compare  the  venation  of  a  number  of  monocotyle- 
dons,   e.g.    Tradescantia,    Alisma,    Sagittaria,    Pontederia, 
Calla,  Arissema,  Smilax.      Draw  accurately  one  or  more 
leaves. 

III.  Examine    the  venation  of   the  leaves  of  Catalpa, 
Liriodendron,    Fuchsia,    and    Nymphsea.       How   does    it 
compare  from  a  mechanical  standpoint  with  that  of  the 
leaves  previously  studied  ? 

IV.  Study  critically  the  structure  of  the  leaf  of  a  black 
oak  or  red  oak.     Measure  the  widest  space  you  can  find 


THE   LEAF.  63 

that  is  free  from  veinlets.     Do  these  end  freely  or  anas- 
tomose ?     Is  there  any  apparent  advantage  in  this  ? 

Assimilation. 

The  chief  and  characteristic  function  of  green  leaves  is 
assimilation,  that  is,  the  production  of  organized  food  sub- 
stances. 

I.  Examine  the  leaves  of  Elodea  Canadensis  under  the 
compound  microscope.     Study  the  form  and  position  of 
the  chlorophyll  bodies  contained  in  the  cells.     Are  they 
equally  numerous  in  all  parts  of  the  leaf  ?     Draw  two  or 
more  cells  showing  the  chlorophyll  bodies  in  place.     Com- 
pare with  these  the  chlorophyll  bodies  of  Mnium  or  other 
common  moss. 

II.  Take   fresh  leaves   of   the   Elodea    that   has   been 
growing  in  a   jar  of  water  exposed   to  sunlight.      Place 
them  in  strong  alcohol  and  allow  them  to  remain  until 
they  have  lost   their  color  and   the    alcohol   has   turned 
green.     Mount  for  microscopic  study  and  test  with  iodine 
solution.      Starch   should    be   found    in   the   chlorophyll 
bodies.     It  may  be  demonstrated  still  more  easily  in  the 
chlorophyll   bands    of    Spirogyra    and    other   filamentous 
algse. 

III.  By  an  experiment  best  performed  by  the  teacher 
or  by  a  pupil  specially  appointed,  the  necessity  of  light  for 
the  production  of  starch,  and  the  local  nature  of  the  pro- 
cess  of   assimilation   is   demonstrated.      Take    a   healthy 
Tropseolum  (u  nasturtium  ")  growing  in  a  flower  pot,  and 
place  it  in  the  dark  for  two  or  three  days.     Test  one  of 
the  leaves  for   starch,  which  by  this    time  should   have 
disappeared.     Now  place  the  plant  where  it  will  be  exposed 
to  the  bright  sunlight,  having  previously  covered  a  part  of 


64  STUDY   OF   COMMON   PLANTS. 

one  or  more  of  the  leaves  so  as  to  exclude  the  light  by 
pinning  flat  pieces  of  cork  closely  on  opposite  sides.  After 
the  plant  has  been  in  the  light  for  a  day  or  more,  proper 
tests  show  that  starch  has  been  formed  in  the  parts  of  the 
leaves  exposed  to  light  but  is  absent  where  they  were 
covered  (except  in  the  fibro-vascular  bundles).  Further 
details  are  given  by  Detmer,  Das  pfiamenphysiologische 
Praktikum,  pp.  33-34  and  3T-38. 

IV.  Place  an  inverted  funnel  over  a  lot  of  Elodea, 
growing  in  a  glass  jar,  and  push  it  down  until  the  small 
end  of  the  funnel  is  beneath  the  surface  of  the  water. 
Fill  a  test-tube  with  water,  stop  it  with  the  thumb,  invert, 
and  (under  water)  bring  the  small  end  of  the  funnel  into 
it.  Set  the  apparatus  where  it  will  be  in  bright  sunlight. 
Observe  the  bubbles  of  gas  given  off  by  the  plant.  After 
enough  has  been  collected  in  the  tube,  test  for  oxygen. 
This  may  be  done  by  lighting  a  match  and  blowing  it  out, 
and  then  inserting  it,  while  still  glowing,  into  the  test- 
tube. 

Y.  The  preceding  observations  show  that  starch  is 
formed  in  the  chlorophyll  bodies  in  the  presence  of  sun- 
light, and  that  during  the  process  oxygen  is  given  off. 
By  means  of  a  simple  experiment  it  may  also  be  shown 
that  starch  is  not  thus  produced  unless  carbon  dioxide  is 
supplied  to  the  plant.  The  teacher  will  find  the  apparatus 
figured  and  described  by  Detmer,  Praktikum,  p.  38,  easily 
made  and  entirely  satisfactory. 

Transpiration. 

I.  Take  a  quantity  of  green  leaves  and  place  them  in  a 
wide-mouthed  bottle.  After  a  time  observe  the  moisture 
that  has  collected  on  its  inner  surface.  Where  has  it 
come  from  ? 


THE   LEAF.  65 

II.  Cut  off  a  strong,  well-developed  leaf  of  a  primrose, 
immerse  the  blade  of  the  leaf  in  water,  and  placing  the 
cut  end  of  the  petiole  in  the  mouth,  inhale  forcibly.     Do 
you  obtain  any  proof  that  the  inside  of  the  leaf  is  in  com- 
munication with  the  atmosphere  ? 

III.  Take  any  leafy  plant  of  convenient  size  that  is 
growing  in  a  flower  pot,  cover  the  pot  with  a  piece  of 
dentists'  rubber,  bringing  it  up  around  the  stem  of  the 
plant   and   tying   it   so  that   no  water  can  be  given  off 
except  through  the  plant  itself.     Weigh  the  whole,  and  at 
the  end  of  twenty-four  hours  weigh  again.     To  what  is  the 
loss  of  weight  due  ? 

IV.  Vary  the  last   experiment  by  employing  different 
kinds  of  plants,  as,  for  example,  some  with  leathery  and 
others  with  soft  leaves ;  also  by  placing  some  in  the  sun- 
light and  others  in  the  shade,  in  the  open  air  and  in  a 
closed  room.     What  are  some  of  the  conditions  affecting 
transpiration  ? 

Respiration. 

Respiration  is  a  function  of  every  living  cell.  Hence 
leaves  are  to  be  thought  of  as  organs  of  respiration  in  so 
far  as  they  expose  a  very  large  number  of  active  cells  to 
the  atmosphere,  although  they  do  not  really  "  correspond 
to  the  lungs  of  animals."  We  may  therefore  employ 
leaves  to  demonstrate  the  process  of  respiration,  or  we 
may  use  flowers  or  germinating  seeds. 

Take  three  wide-mouthed  bottles  and  fill  each  two-thirds 
full,  the  first  of  fresh  leaves,  the  second  of  germinating 
peas,  and  the  third  of  flowers.  Cork  and  allow  to  stand  a 
few  hours.  Test  the  air  in  the  bottles  at  the  beginning 
and  close  of  the  experiment  by  introducing  a  homoeopathic 
vial  containing  limewater,  also  by  inserting  a  lighted 
match.  What  is  the  result? 


66  STUDY  OF   COMMON   PLANTS. 

NOTE.  —  The  student  should  carefully  consider  what  is  taking  place  in 
the  cells  of  green  leaves,  inasmuch  as  a  great  deal  of  confusion  has  arisen 
through  lack  of  clear  conception  and  expression.  Since  they  respire  like 
other  parts  of  the  plant,  leaves  absorb  oxygen  and  give  off  carbon  dioxide 
both  day  and  night.  On  the  other  hand,  as  organs  of  assimilation,  they 
decompose  carbon  dioxide  in  the  sunlight,  giving  off  oxygen  and  employ- 
ing the  carbon  in  the  production  of  starch.  A  complete  discussion  of  the 
subject  would  require  much  space,  but  the  fundamental  facts  are  as 
stated  above,  and  should  be  firmly  fixed  in  mind. 


MODIFIED    LEAVES. 

When  some  other  function  than  that  of  assimilation 
becomes  predominant,  leaves  exhibit  marked,  and  in  some 
cases  extremely  peculiar,  modifications. 

I.  Examine  shoots  of  the  common  barberry.    Determine 
the  morphology  of  the  spines  and  give  reasons.     Compare 
the  spines    of   the    common  locust.     Are   they  the  same 
morphologically  as  those  of  the  barberry  ?     Examine  dif- 
ferent species  of  cacti  and  determine  the  morphology  of 
the  parts. 

II.  Study  the  tendrils  of  such  of  the  following  plants  as 
can  be  obtained  and  ascertain  which  of  them  are  to  be 
classed  as  leaves  or  parts  of  leaves:  Smilax  rotundifolia, 
Cobcea    scandens,   Adlumia    cirrhosa,    Echinocystis    lobata, 
grape-vine,  pea,  cucumber,  etc.    Note  particularly  any  cases 
in  which  only  partial  modification  has  taken  place.     Cf. 
Darwin,  Climbing  Plants,  Chaps.  Ill,  IV. 

III.  Leaves    of    insectivorous    plants.       See    Special 
Studies. 

SPECIAL    STUDIES. 

I.  Correlation  of  the  forms  of  leaves  with  their  position 
on  the  stem.  See  Lubbock,  Flowers,  Fruits,  and 
Leaves. 


THE  LEAF.  67 

II.  Extent  of  leaf  surface.  Measure  accurately  the 
superficial  area  of  an  average  leaf  of  a  geranium  or 
other  common  plant,  and  estimate  its  entire 
leaf  surface. 

III.  Generic  and  specific  characters  drawn  from  leaves. 

IV.  Variability.     Compare  the  leaves  of  any  individual 

plant,  a  rose  bush,  for  example,  and  observe  their 
different  forms. 

V.  Leaves  of  insectivorous  plants.  Drosera  rotundifolia 
is  widely  distributed  and  is  easily  cultivated  in  the 
laboratory.  It  is  a  most  valuable  plant  for  pro- 
longed observation  and  experiment.  Cf.  Darwin, 
Insectivorous  Plants. 


REVIEW    AND    SUMMARY. 

The  leaf  is  the  most  characteristic,  and,  in  some  respects, 
the  most  important  part  of  the  plant.  The  venation  and 
various  peculiarities  of  form  and  structure  are  . 

^  A  cnaracter- 

usually  sufficient  to  indicate  at  once  the  class,  isticpartof 
and  not  infrequently  the  genus  or  species  to  thePlantl 
which  a  plant  belongs.  Even  those  who  have  had  no 
special  botanical  training  readily  distinguish  the  oak, 
willow,  maple,  and  various  other  plants  by  the  leaf  alone. 
Hence  in  determining  relationships  special  attention  is 
given  to  characters  drawn  from  leaves,  and  it  becomes 
necessary  to  define  these  with  care  and  precision.  Physio- 
logically, too,  the  leaf  is  engaged  in  work  peculiar  to 
plants,  work  of  a  nature  that  cannot  be  performed  by 
animals,  and  upon  which  they  are  dependent  for  their 
continued  existence  on  the  globe.  A  clear  conception, 


68  STUDY   OF   COMMON   PLANTS. 

therefore,  of  the  general  facts  of  leaf  structure  and  physi- 
ology is  essential  to  an  understanding  of  some  of  the  most 
fundamental  facts  of  biological  science. 

Beginning  with  form  and  position,  we  have  seen  that, 
as  a  rule,  leaves  are  so  constructed  and  placed  as  to  secure 
Form  and  ^ie  exposure  of  a  large  surface  to  the  air  and 
position,  light.  The  blade  of  the  leaf  is  raised  on  a 
petiole  whenever  this  is  necessary  to  more  readily  accom- 
plish the  end  to  be  attained.  Furthermore,  the  position  of 
leaves  on  the  stem  is  such  as  to  aid  in  securing  the  great- 
est exposure.  If  we  inspect  a  large  tree  in  full  foliage, 
such  as  a  maple  or  bass  wood,  it  will  be  seen  that  the  leaves 
are  placed  so  as  to  result  in  a  minimum  of  interference 
with  each  other.  It  will  also  be  noticed,  as  Sir  John 
Lubbock  points  out,  that  there  is  a  manifest  correlation 
between  the  form  of  the  leaves  and  their  arrangement  on 
the  branch,  so  that  in  many  cases  it  would  be  a  decided 
disadvantage  to  replace  the  leaves  of  one  species  by  those 
of  another  unless  the  leaf  arrangement  were  changed. 
Further,  an  examination  of  buds  that  have  not  yet  opened 
shows  that  the  leaf  arrangement  is  such  as  to  economize 
space.  These  two  principles,  compact  disposition  in  the 
bud,  and  a  position  on  the  stem  that  will  secure  full  expos- 
ure of  leaf  surface,  are  the  determining  factors  in  the 
arrangement  of  leaves.1 

An  examination  of  the  anatomical  structure  of  an  ordi- 

1  Incidentally  it  results  that  the  leaf  arrangement  of  many  plants  is  so 
definitely  fixed  that  it  may  be  expressed  by  a  mathematical  formula. 
Phyllotaxis,  however,  as  usually  presented,  is  a  curious  rather  than  a 
fruitful  study.  "We  must  now  acknowledge  that  there  is  no  general 
law  which  can  be  formulated  for  the  arrangement  of  the  organs  on  a 
parent  axis  ;  that,  on  the  contrary,  according  to  circumstances  in  each 
case,  special  causes  determine  whether  the  relations  of  position  turn  out 
to  be  this  or  that."  —  SACHS,  Physiology  of  Plants,  pp.  500,  501. 


THE   LEAF.  69 

nary  foliage  leaf  shows  that  both  surfaces  are  protected  by 
an  external  layer  of  cells  constituting  the  epi-  ^.  . 
dermis.  The  outer  wall  of  the  epidermal  cells  structure, 
is  commonly  thickened,  and  by  taking  on  a  EPldemis> 
layer  of  cutin  or  wax  becomes  nearly  or  quite  impervious 
to  water.  The  leaves  of  some  plants,  particularly  of  species 
growing  in  tropical  regions,  have  more  than  one  layer  of 
cells  composing  the  epidermis,  thus  securing  more  efficient 
protection.  The  cells  of  the  epidermis  are,  for  the  most 
part,  destitute  of  chlorophyll,  but  contain  a  large  quantity 
of  water  which  is  absorbed  as  required  by  the  delicate  cells 
in  the  interior  of  the  leaf.  Additional  protection  is  often 
afforded  by  hairs  which  thickly  cover  the  leaves  of  many 
species,  particularly  those  growing  on  the  steppes  and 
other  parts  of  the  globe  where  vegetation  is  subject  to 
sudden,  and  extreme  changes  of  temperature.  Finally, 
protection  is  not  infrequently  secured  by  diminishing  the 
amount  of  leaf  surface,  as  seen  in  many  shrubs,  and  in 
desert  grasses  and  sedges  with  cylindrical  leaves. 

Communication  with  the  interior  of  the  leaf  is  secured 
by  means  of  numerous  openings  called  stomata.  These 
are  provided  with  guard-cells,  commonly  of  the 

,    .  '   ,       ,          .  \,    ,       -  Stomata, 

same  general  lorm  as  those  ot  the  hyacinth  leaf, 
which  act  as  a  valve,  opening  in  sunlight  while  the  leaf  is 
at  work  and  closing,  or  partially  closing,  at'  night.  The 
mechanism,  apparently  simple,  is,  in  reality,  rather  diffi- 
cult of  complete  explanation.1  The  essential  fact  is  that 
by  means  of  the  stomata  a  free  interchange  of  watery 
vapor  and  gases  between  the  interior  of  the  leaf  and  the 
surrounding  atmosphere  is  effected,  and  that  by  means 
of  the  guard-cells  this  interchange  is  obstructed  when  the 
external  conditions  are  unfavorable. 

1  Cf .  Sachs,  Physiology  of  Plants,  pp.  248-251. 


70  STUDY   OF   COMMON   PLANTS. 

The  internal  structure  of  the  great  majority  of  leaves 
is  essentially  the  same  as  we  have  seen  in  the  English  ivy. 
Fibro-vascu-  The  midrib  and  veins,  composed  of  fibers  and 
lar  bundles,  tracheids,  present  a  strong  frame-work  by  means 
of  which  all  the  parts  are  supported,  and  which  also  serves 
as  the  conducting  system  of  the  leaf.  The  green  parts 
consist  of  chlorophyll-bearing,  parenchyma  cells,  the  chief 
function  of  which  is  the  manufacture  of  organized  food 
substances.  An  extended  comparison  of  the  leaves  of 
Assimilating  many  species  of  plants  shows  several  interesting 
cells.  arrangements  for  bringing  the  assimilating  cells 

into  an  advantageous  position  as  regards  the  light.  In  the 
first  place,  the  leaf  itself  "  turns  towards  the  light,"  i.e. 
places  itself  so  that  the  upper  surface  is  perpendicular  to 
the  incident  rays.  In  the  second  place,  the  palisade  cells 
are  themselves  nearly  perpendicular  to  the  leaf  surface,  a 
position  in  which  their  contents  are  brought  into  relation 
with  the  light,  without,  however,  cutting  it  off  entirely 
from  the  cells  below.  Finally,  the  chlorophyll  bodies 
vary  their  position  in  the  cells  according  to  the  intensity 
of  the  light,  ranging  themselves  so  as  to  expose  as  large  a 
surface  as  possible  when  the  illumination  is  feeble,  and  a 
less  surface  when  it  is  too  intense.1  In  addition  to  these 
arrangements  with  reference  to  light,  the  assimilating  cells 
are  grouped  in  such  a  manner  as  to  facilitate  the  convey- 
ance of  water  to  them  by  the  fibro-vascular  bundles,  and 
the  removal  of  elaborated  food  substances  through  the 
same  channels.2 

It  is  thus  seen  that  the  leaf  is  an  extremely  delicate 
organ,  adapted  to  the  performance  of  certain  important 
functions.  Their  first  and  most  characteristic  function 

1  Sachs,  I.e.,  p.  617  et  seq. 

2  Haberlandt,  Physiologische  Pflanzenanatomie,  p.  184  et  seq. 


THE  LEAF.  71 

is  the  formation  of  organic  food  products  out  of  the  crude 
substances  taken  in  from  the  atmosphere  and  Functions. 
soil.  In  the  presence  of  sunlight  starch  is  Assimilation, 
produced  in  the  chlorophyll  bodies.  The  materials  from 
Avhich  it  is  formed  are  carbon  dioxide,  obtained  from 
the  atmosphere,  and  water  brought  up  from  the  roots. 
The  starch  accumulates  in  the  daytime  in  the  cells  where 
it  is  formed,  and  afterwards  is  conveyed  away  in  a  soluble 
form  to  the  various  reservoirs  of  reserve  materials.  Simple 
experiments  have  shown  the  conditions  under  which  the 
formation  of  starch  takes  place  and  the  attendant  phe- 
nomena. The  rapid  evolution  of  oxygen  seen  when  a 
water  plant  is  allowed  to  stand  in  'bright  sunlight  is  at 
once  checked  when  the  vessel  containing  it  is  brought 
into  the  shade.  The  oxygen  is  given  off  in  the  formation 
of  starch  arid  this  process  ceases  when  light  is  wanting. 
Again,  if  the  water  in  which  the  plant  is  growing  is  boiled 
so  as  to  expel  the  carbon  dioxide,  it  is  observed  that  the 
evolution  of  oxygen  ceases  as  in  the  preceding  experiment, 
but  for  a  different  reason.  The  carbon  dioxide  being 
wanting,  the  leaves  are  deprived  of  the  carbon  necessary 
to  the  production  of  starch. 

Water  in  relatively  large  quantities  is  required  to  carry 
to  the  leaf,  and  to  the  other  parts  of  the  plant,  the  sub- 
stances used  in  the  formation  of  starch  and  Transpira- 
other  products.  The  surplus  water  is  evapo-  tion' 
rated  by  the  leaves.  By  simply  weighing  at  stated  inter- 
vals a  plant  arranged  so  that  evaporation  can  take  place 
from  no  other  part,  it  is  found  that  large  amounts  of 
watery  vapor  are  given  off  through  the  leaves.  Transpira- 
tion, then,  or  the  evaporation  of  water,  is  another  important 
function  of  leaves,  since  the  water  thus  given  off  is  the 
vehicle  of  transportation  of  the  various  substances  used  by 
the  plant, 


72  STUDY   OF   COMMON   PLANTS. 

Still  another  function  which  the  leaf  shares  with  other 

living  parts  of  the  plant,  and  which  is  characteristic  of  all 

living  cells  whether  plant  or  animal,  is  that  of 

Respiration,  .      _.  I  ,,  , 

respiration.  As  we  have  seen,  one  ot  the  prod- 
ucts of  respiration,  carbon  dioxide,  is  easily  demonstrated 
by  testing  with  limewater  the  air  within  a  bottle  contain- 
ing a  quantity  of  green  leaves.  The  abundant  precipitate 
of  carbonate  of  lime  shows  that  the  leaves  are  giving  off 
carbon  dioxide  in  considerable  quantity,  and  as  this  is  true 
whether  the  experiment  is  performed  in  the  daytime  or  at 
night,  we  infer  that  respiration  is  going  on  continually. 
It  should  be  said,  however,  that,  contrary  to  a  widely 
spread  popular  belief,  the  quantity  of  carbon  dioxide 
exhaled  by  plants  is  so  small  in  comparison  with  what  is 
given  off  in  animal  respiration  that  it  may  be  disregarded 
in  connection  with  the  question  of  keeping  house  plants. 
They  are  a  decided  advantage  in  the  home  from  a  sanitary, 
as  well  as  aesthetic,  point  of  view. 

The  chief  functions  of  the  leaf,  then,  are 

1.  Assimilation,  or  the  production  of  organized  material. 

2.  Transpiration,  or  the  evaporation  of  water  that  has 
served  as  a  vehicle  for  the  transportation  of  crude  sub- 
stances. 

3.  Respiration,  a  process  common  to  all  living  things. 

The  first  of  these  takes  place  in  sunlight,  or  its  equiva- 
lent ;  the  second  is  most  active  in  the  daytime,  but  is  not 
limited  to  it ;  and  the  last  continues  both  day  and  night, 
as  long  as  the  leaf  is  alive. 

We  have  learned  in  our  study  of  the  barberry  and  a 
number  of  other  familiar  plants,  that  leaves  are  subject  to 
various  modifications  corresponding  to  other  than  their 
ordinary  functions.  These  modifications  are  not  infre- 


THE   LEAF.  73 

quently  so  profound  that  it  becomes  a  matter  of  no  little 
difficulty  to  pronounce  upon  the  morphological  Modified 
character  of  a  particular  structure.  Spines  leaves- 
and  tendrils,  for  example,  may  represent  either  leaves  or 
branches.  The  morphological  character  of  bud-scales,  on 
the  other  hand,  is  usually  recognized  at  once  from  their 
position,  structure,  and  especially  from  the  various  transi- 
tional forms  by  which  they  are  connected  with  ordinary 
leaves.  Though  often  puzzling,  the  morphology  of  modi- 
fled  leaves  is  always  an  exceedingly  interesting  and  profit- 
able study.1 

1  Cf.  Gray,  Structural  Botany,  pp.  110-118. 


74  STUDY   OF   COMMON   PLANTS. 


VI.   THE   FLOWER. 

MATERIAL   REQUIRED. 

Flowers  of  white  Trillium,  T.  grandiflorum,  Salisb.    Other  species  may 

be  used. 
Cultivated  Fuchsia.   Specimens  must  be  selected  that  have  not  become 

double. 
Several  pots  of  cultivated  primroses  in  flower,  some  specimens  with 

long-  and  others  with  short-styled  flowers. 
Various  wild  flowers,  or  cultivated  kinds  that  have  not  undergone 

modification,  may  be  substituted  for  the  preceding. 

TRILLIUM.      T.  grandiflorum,  Salisb. 

I.    Study  first  the  morphological  characters.1 

1.  Is  the  flower  complete,  that  is,  are  the  calyx,  corolla, 

stamens,  and  pistil  all  present  ? 

2.  What  is  the  numerical  plan  as  indicated  by  the  num- 

ber of  sepals,  petals,  stamens,  and  carpels  ? 

3.  Is  the  flower  regular  ? 

4.  Is  coalescence  to  be  observed  in  the  members  of  any 

whorl  ? 

5.  Describe  in  detail  each   part    of   the  flower,  noting 

shape,  color,  and  other  features. 

II.  Make  a  transverse  section  of  the  ovary.  Draw  it 
sufficiently  enlarged  to  show  all  the  parts  clearly.  Note 
particularly  the  form,  position,  and  place  of  attachment 

1  Read  Gray,  Lessons,  pp.  79-117. 


THE  FLOWER.  75 

of  the  ovules,  and  make  out  as  much  of  their  structure  as 
possible. 

III.  Construct  a  diagram  of  the  flower.1 

NOTE.  —  A  correct  diagram  necessitates  a  careful  study  of  the  relation 
of  every  part  of  the  flower  to  every  other  part.  It  should  be  drawn  with 
geometrical  precision,  representing  the  parts  of  each  whorl  so  as  to  show 
their  number,  arrangement,  relation  to  other  whorls,  and  to  some  extent 
their  union  or  separation.  Properly  constructed,  such  diagrams  serve 
an  important  purpose  by  facilitating  the  comparison  of  the  permanent 
morphological  features  of  flowers  of  the  same  and  different  families. 

IV.  Ascertain  whether  the.  flower  manifests  any  physio- 
logical adaptations. 

1.  Is  there  anything  protective  in  its  form,  position,  or 

structure  ? 

2.  Enumerate  its  attractive  features. 

3.  Is  there  anything  to  indicate  whether  cross-  or  self- 

fertilization  takes  place  ? 

NOTE.  —  A  satisfactory  answer  to  this  question  may  require 
more  experience  than  the  pupil  has  yet  attained.  It  involves 
close  observation  of  any  peculiarities  that  seem  to  favor  the  visits 
of  insects  or  other  agents  of  fertilization,  such  as  grooves,  guiding 
lines,  the  presence  of  nectar,  and  so  on.2 

FUCHSIA.     Fuchsia  coccinea,  etc. 

I.    Note  carefully  all  external  features,  such  as 

1.  Position   of    the   flower  and   its    direction,   erect  or 

drooping.     Compare  with  the  flower  buds. 

2.  Color  of  different  whorls. 

3.  Union  of  parts 

a.  Of  the  same  whorl. 

b.  Of  different  whorls. 

1  Cf.  Gray,  Lessons,  p.  82,  footnote  ;  also  Eichler,  Bluthendiagramme. 

2  Cf .  Miiller,  Fertilization  of  Flowers. 


76  STUDY   OF   COMMON   PLANTS. 

4.  The  extremely  long  style. 

5.  Relative  position  of  anthers  and  stigma. 

6.  Numerical  plan. 

II.  Make    a   clean    transverse    section    of    the    ovary. 
Examine  under   the    dissecting   microscope.     How  many 
carpels  are  there  ? 

III.  Draw  the  section,  taking  care  to  represent  accu- 
rately 

1.  The  position  of  septa  and  placentae. 

2.  Attachment  and  form  of  ovules. 

IV.  Make  an  exact  longitudinal  section  and  draw  it  in 
outline.     Note  particularly 

1.  The  conspicuous  nectary. 

2.  Presence  or  absence  of  nectar. 

3.  The  insertion  of  the  filaments  and  their  direction,  so 

placed  as  to  bar  out  unwelcome  visitors. 

V.  Measure  the  length  of  the  calyx  tube.     Is  the  nectar 
accessible  to  bees  and  similar  insects  ? 

VI.  Construct  a  diagram. 

VII.  Review  the  whole  and  describe  in  detail. 

PRIMROSE.     Primula  veris,  etc. 

I.    Study  the  morphological  characters,  such  as 

1.  The  numerical  plan. 

2.  Regularity. 

3.  Symmetry. 

4.  Coalescence  of  parts. 

5.  Structure  of  ovary. 

II.    Construct  a  diagram. 


THE  FLOWER.  77 

III.  Note  all  protective  and  attractive  arrangements. 

IV.  Compare  flowers  of  a  number  of  different  plants 
with  regard  to  the  position  of  the  essential  organs.     Notice 

1.  The  length  and  insertion  of  the  stamens. 

2.  Length  of  style. 

3.  Form  and  structure  of  the  stigma. 

4.  Any  other  particulars  in  which  the  long-  and  short- 

styled  forms  differ. 

V.  Make  longitudinal  sections   of  the  two  forms  and 
sketch   in    outline.      Read    Darwin,    Different    Forms    of 
Flowers  on  Plants  of  the  Same  Species,  Chap.  I. 

NOTE. — It  will,  of  course,  be  understood  that  an  acquaintance  with 
many  more  species  will  be  necessary  in  order  to  obtain  a  general  concep- 
tion of  the  morphology  of  the  flower,  and  an  adequate  knowledge  of  its 
physiological  adaptations.  Accordingly,  similar  studies  of  other  flowers 
may  be  made  before  proceeding  farther,  or  this  may  be  postponed  until 
the  families  of  flowering  plants  are  taken  up.  In  any  case  the  student 
should  now  read  carefully  Gray,  Lessons,  pp.  79-109,  or  the  equivalent 
part  of  the  Structural  Botany,  by  the  same  author.  He  should  also  make 
a  constant  practice  of  referring  to  Miiller,  Fertilization  of  Flowers. 

POLLEN,    OVULES,   EMBRYO. 

I.  Examine  with  the  compound  microscope  the  pollen 
of  a  number  of  different  plants,  such  as  pine,  lily,  pump- 
kin, mallow,  and  others.     Compare  the  grains  as  to  size, 
shape,  and  surface.     Notice  whether  those  disseminated  by 
the  wind  are  characterized  by  different  features  from  those 
that  are  carried  by  insects  or  birds.     Draw  and  describe. 

II.  Sow  various  kinds  of  pollen  in  watch  glasses  con- 
taining sugar  solution  (3  to  20  per  cent).     At  intervals  of 
a  day  or  less  transfer  a  few  grains  to  the  glass  slide  with 
a  camel's-hair  brush  and  examine  microscopically.     Some 


78  STUDY   OF   COMMON   PLANTS. 

of  them  will  soon  show  formation  of  pollen-tubes.     Draw 
them  in  different  stages  of  development.1 

III.  Cut  transverse  sections  of  the  ovary  of  Trillium  at 
the  time  the  flower  is  fading  and  at  subsequent  periods. 
Under   the   compound    microscope    study   the    ovules   in 
different  stages  of  growth.     Notice 

1.  The  anatropous  form  of  the  ovule. 

2.  Its  two  coats  distinctly  marked  at  the  apex. 

3.  The  nucellus,  or  mass  of  tissue  making  up  the  body 

of  the  ovule. 

4.  The  micropyle,  a  canal  leading  from  the  apex  of  the 

ovule  to  the  nucellus. 
Draw  and  describe. 

IV.  Prepare  similar  sections  of  the  ovary  of  Fuchsia, 
Begonia,  and  various  other  plants,  studying  carefully,  as 
before,  the   structure  of  the  ovule.     Some  of  these  will 
show,  lying  within  the  nucellus,  the  outlines  of  the  embryo- 
sac,  a   large  cell   in  which   the   embryo   is   subsequently 
formed.      Clearing    with    potash   solution   facilitates    the 
observation.      Indian-pipe,  Monotropa   uniflora,    L.,  when 
it  can  be  obtained,  is  an  extremely  favorable  species  for 
the  study  of  the  embryo-sac  and  the  structures  contained 
in  it.2 

V.  Take   a    flower-bud    of    shepherd's-purse,    Capsella 
Bursa-pastoris,  Mcench,  and  under  a  lens  remove  the  floral 
envelopes.      Open  the  ovary  and  dissect  out  the  ovules. 
Treat  on  the  slide  with  dilute  potash  solution  and  apply 
light  pressure  to  the  cover  glass.     If  a  series  of  younger 

1  For  further  hints  as  to  culture  methods,  cf.  Strasburger  and  Hill- 
house,  Practical  Botany,  p.  320  c ;  Halsted,  Bot.  Gaz.  XII  (1887), 
p.  287. 

2Cf.  Strasburger  and  Hillhouse,  I.e.,  pp.  327-337. 


THE   FLOWER.  79 

and  older  specimens  are  prepared  in  this  way,  the  embryo 
in  various  stages  of  development  can  be  satisfactorily 
studied.  Make  a  series  of  sketches  showing  as  many  of 
these  stages  as  practicable.  Compare  your  own  figures 
with  those  of  Hanstein.1  Write  a  brief  account  of  the 
development  of  the  embryo  of  this  plant  as  far  as  you 
have  observed  it. 

SPECIAL   STUDIES.2 

I.  Morphology  of  stamens. 

II.  Morphology  of  the  pistil. 

III.  Protection  against  unbidden  guests. 

IV.  Dimorphism. 

V.  Mechanical  devices  favoring  cross-fertilization. 

VI.  Changes  in  the  ovule  after  fertilization. 

REVIEW   AND    SUMMARY.3 

In  the  preceding  study  we  have  found  that  a  flower  is 
commonly  made  up  of  four  distinct  whorls,  or  circles, 
calyx,  corolla,  stamens,  and  pistil.  The  parts  part8  Of  the 
of  the  calyx  are  called  sepals,  those  of  the  cor-  floweri 
olla,  petals.  The  stamens  are  spoken  of  collectively  as  the 
androecium,  and  the  pistil  (or  pistils)  as  the  gynsecium. 
While  in  most  flowers  all  the  parts  are  present,  there  are 

1  Goebel,  Outlines  of  Classification  and  Special  Morphology,  p.  397. 

2  Gray,  Structural  Botany,  pp.  215-240,  251-268  ;  Kerner,  Flowers  and 
their  Unbidden  Guests;   Darwin,  Different  Forms  of  Flowers  on  Plants 
of  the  Same  Species;  Strasburger  and  Hillhouse,  Practical  Botany,  pp. 
311-337. 

3  It  will  probably  be  better  to  postpone  the  review  until  the  flowers  of 
a  considerable  number  of  families  have  been  carefully  studied.     After 
this  has  been  done  the  pupil  may  profitably  devote  some  little  time  to  the 
resume  and  references  here  given. 


80  *  STUDY   OF   COMMON   PLANTS. 

many  species  in  which  one  or  more  of  the  whorls  are 
absent,  and  each  is  subject  to  more  or  less  modification 
of  form  and  structure. 

Morphologically  the  flower  is  to  be  regarded  as  a  modi- 
fied branch,  the  members  of  its  different  whorls  corre- 
Its  morphol-  spending  to  so  many  leaves.  The  most  obvious 
°sy-  reasons  for  this  view  are  that  the  flower  has  the 

position  of  a  branch;  that  the  arrangement  of  its  parts 
follows  more  or  less  strictly  that  of  the  leaves  on  the  stem ; 
that  the  anatomy  of  leaves  and  floral  structures  is  essen- 
tially the  same ;  that  transitions  from  ordinary  leaves  to 
floral  envelopes  are  of  frequent  occurrence ;  and  finally 
that  reversions  of  parts  of  the  flower  to  a  more  primitive  or 
leaf -like  form  often  take  place. 

It  is  convenient,  and  at  the  same  time  in  accordance 
with  the  viewrs  now  held  regarding  the  actual  evolution  of 
Typical  plant  life,  to  take  some  such  flower  as  that  of 
flower,  the  Trillium  as  a  pattern  or  "typical"  flower 

with  which  to  compare  others.  The  Trillium,  as  we  have 
seen,  has  three  distinct  green  sepals,  three  petals,  two 
whorls  of  stamens  of  three  each,  and  a  pistil  composed  of 
three  parts,  each  part  called  a  carpel.  We  may  character- 
ize our  pattern  flower,  then,  as  having  all  the  parts  present, 
these  parts  distinct  from  each  other,  of  the  same  form  and 
size  in  each  whorl,  and  presenting  throughout  the  same 
numerical  plan,  most  frequently  three  or  five.  In  other 
words,  it  exhibits  completeness,  distinctness  of  parts,  regu- 
larity, and  symmetry.1 

The  flowers  of  most  plants  differ  in  one  or  more  respects 
from  such  a  typical  flower  as  has  been  described.  Never- 

1  The  flower  of  Trillium  departs  slightly  from  the  ideal  typical  flower 
in  the  coalescence  of  the  three  carpels  to  form  the  compound  ovary.  Cf. 
Gray,  Structural  Botany,  pp.  176-178. 


THE   FLOWER.  81 

theless  a  comparison  of  the  flower  of  a  given  species  as  we 
actually  find  it,  is,  as  a  rule,  readily  made  with 

-  ,          .  .  Modifications, 

tlie   assumed   type,   and   this   comparison   is  a 
necessaiy  part  of  the  morphological  study  of  any  flower. 
In  carrying  out  such  a  study  it  is  found   that  flowers 
may  vary  from  the  type  in  any  one  (or  in  more  than  one) 
of  its  characteristic  features.     In  the  first  place, 

i  r    ,1  11-  T       <•    i     •          Coalescence, 

members  ot  the  same  whorl,  instead  01  being 
separate,  may  be  more  or  less  completely  united.  The 
calyx  of  the  primrose,  the  bell-shaped  corolla  of  the  cam- 
panula, the  united  filaments  of  various  members  of  the 
pea  family,  and  the  compound  ovary  of  the  lily,  are 
familiar  examples.  Coalescence  of  parts  is  held  by  bota- 
nists to  indicate  a  higher  development  than  has  been 
attained  by  flowers  in  which  the  parts  remain  free. 

A  still  further  step  in  the  same  direction  is  seen  in  the 
union  of  contiguous  parts  of  different  circles.  Thus  the 
flower  of  the  Fuchsia  has  the  calyx-tube  so 

,       .  ,       ,  .„    Adnation, 

united  with  the  ovary  as  to  make  it  appear  as  if 
inserted  on  its  summit,  and  both  petals  and  stamens  are 
inserted  on  the  calyx,  the  filaments  showing  very  plainly 
their  union  with  the  calyx-tube.  The  various  degrees  of 
adnation  furnish  important  characters  that  are  constantly 
employed  in  descriptive  botany.1 

Again,  while  the  typical  flower  is  regular,  having  all  the 
parts  of  a  given  whorl  alike  in  size  and  shape,  the  flowers 
of  the  more  highly  developed  species,  as  a  rule, 

T  i     j    •  1      -4-  rpi  -,  n       Irregularity. 

show  marked  irregularity.     Ihe  spurred  corolla 
of  the  violet,  and  the  curiously  irregular  flowers  of  the 
sweet  pea,  salvia,  and  snapdragon  are  striking  cases.     It  is 
believed  that  these  are  descendants  of  much  simpler  forms 

1  Cf.  Gray,  Structural  Botany,  pp.  182-184. 


82  STUDY  OF  COMMON  PLANTS. 

that  in  the  course  of  an  indefinite  period  of  time  have 
gradually  taken  on  shapes  manifestly  correlated  with  the 
visits  of  insects  or  other  agents  by  which  pollen  is  carried 
from  one  flower  to  another. 

Many  flowers  have  undergone  the  suppression  of  one  or 

more  parts.     In  some  cases  a  whole  whorl  is  wanting,  as 

in  the  anemone,  which  is  destitute  of  a  corolla ; 

Suppression,  . 

or  several  whorls  may  be  lacking,  as  in  the  wil- 
lows, the  flowers  of  which  are  reduced  to  a  single  whorl. 
Frequently,  however,  a  part  of  a  whorl  only  is  wanting, 
and  in  such  cases  it  often  happens  that  a  rudiment,  or 
trace,  of  the  missing  parts  remains  to  indicate  a  former 
condition.  In  the  common  toad-flax,  for  example,  there  are 
four  perfect  stamens  and  a  trace  of  the  fifth ;  some  of  the 
mints  now  have  but  two  stamens,  although  five  was  the 
original  number ;  and  many  plants,  as  the  lupine  and  its 
allies,  otherwise  on  the  plan  of  five,  have  the  ovary  reduced 
to  a  single  carpel. 

The  symmetry  of  the  flower  is  interfered  with,  not  only 
by  the  suppression,  but  also  by  the  multiplication  of  parts, 
Multipiica-  so  that  it  not  infrequently  happens  that  the 
tion.  original  plan,  in  some  one  whorl  at  least,  is  no 

longer  recognizable.  The  very  numerous  stamens  of  the 
cacti  will  serve  as  an  illustration. 

The  changes  described  are  of  great  interest  as  indicating 
actual  steps  in  the  developmental  history  of  flowers.  They 
help  us  to  see,  if  not  fully  yet  in  part,  how  such  extraor- 
dinary structures  as  those  of  a  milkweed  flower  or  an 
orchid  have  come  to  be  what  they  are.1 

1  Lack  of  space  renders  it  necessary  to  refer  the  student  to  a  much 
more  extended  discussion  of  the  subject  than  can  here  be  undertaken. 
Cf.  Gray,  Structural  Botany,  pp.  179-209,  which  has  been  followed  in 
the  main  in  the  brief  resume  just  given. 


THE   FLOWER.  83 

As  already  intimated,  the  parts  of  the  flower  exhibit 
the  same  general  structure  as  that  of  the  leaf,  structure  and 
but  with  modifications  corresponding  to  the  Actions  of 

the  several 
special  functions  that  each  part  fulfills.  parts, 

The  calyx  and  corolla  are  protective,  serving  to  guard 
the  parts  within  from  frost  and  rain  and  the  intrusion  of 
unwelcome    visitors.     They  are  also  attractive,  pioraienvei. 
particularly  the   corolla,   which  is  usually  col-  °Pes> 
ored  so  as  to  attract  bees  and  other  color-loving  insects. 
They  form,  too,  a  part  of  the  mechanism,  often  very  pecu- 
liar and  interesting,  by  which  pollination  is  effected. 

The  stamens  are  usually  far   more    modified   than  the 
floral  envelopes.     The  thickened  anther,  corresponding  to 
the  blade  of  the  leaf,  produces  pollen,  the  active 
agent  of  fertilization.      The  pollen    consists  of 
rounded  cells,  the  walls  of  which  are  variously  thickened, 
frequently    beset    with    spines,    and,    in    some    instances, 
winged,  thus  facilitating  their  conveyance  by  insects  or  by 
the  wind.     The  cell  contents  are  protoplasm,  with  one  or 
more  nuclei,  and  a  considerable  quantity  of  food  material, 
such  as  starch,  oil,  and  sugar. 

The  pistil  is  simple  or  compound  according  as  it  is  made 
up  of  one  or  more  than  one  carpellary  leaf.1  The  ovules, 
which  afterwards  become  the  seeds,  originate  as 
cellular  outgrowths  from  the  margins  of  the 
carpel.  An  ovule,  when  fully  formed,  consists  of  a  cen- 
tral mass  of  cells,  called  the  nucellus,  around  which  one, 
or  commonly  two,  protective  coats  are  formed,  and  within 
which  a  cell,  called  the  embryo-sac,  arises.  It  is  in  the 
embryo-sac  that  the  young  embryo  is  developed.  An 
opening  between  the  coats,  called  the  micropyle,  leads 
down  to  the  nucellus.  The  parts  as  described  at  once 

1  Cf .  Gray,  Structural  Botany,  p.  260  et  seq. 


84  STUDY   OF    COMMON    PLANTS. 

recall  the  seed,  which  is  simply  a  fertilized  and  matured 
ovule. 

When  pollen-grains  have  been  brought  by  any  agency 

to  the  moist  and  receptive  stigma  of  a  flower  of  the  same 

species,  they  begin  after  a  short  interval  to  ger- 

Fertilization,          .  T  .  n        ^    i 

minate.  In  germination  pollen-tubes  are  pro- 
duced, which  rapidly  elongate,  growing  through  the  loose 
tissue  of  the  stigma  and  downwards  through  the  style  until 
they  enter  the  ovary.  Here  they  find  their  way  to  the 
ovules,  which  they  enter,  one  pollen-tube  going  to  each 
ovule  and  pushing  its  way  through  the  micropyle,  until  its 
end  comes  in  contact  with  the  nucellus  and  finally  with 
the  embryo-sac.  A  portion  of  the  contents  of  the  pollen- 
tube,  including  nuclear  material,  now  passes  into  the 
embryo-sac  and  unites  with  a  cell  in  it,  called  the  oosphere. 
The  oosphere  now  takes  on  a  cell-membrane,  increases  in 
size,  undergoes  division,  and,  as  a  result  of  still  further 
division  and  growth,  produces  the  embryo.  Other  cells 
are  formed  in  the  embryo-sac  which  rapidly  multiply  and 
become  the  endosperm,  a  tissue  often  absorbed  afterwards 
by  the  growing  embryo  prior  to  germination.  Meantime 
the  embryo-sac  becomes  many  times  its  former  size,  while 
the  nucellus  is  crowded  to  the  walls  of  the  ovule  and  is 
commonly  absorbed,  but  sometimes  remains  as  the  peri- 
sperm.  The  coats  of  the  ovule  are  extended  to  keep  up 
with  this  increase  in  size,  the  testa  takes  on  its  character- 
istic hard  and  usually  colored  condition,  a  further  store  of 
food  is  deposited  around  or  in  the  growing  embryo,  and 
with  the  completion  of  these  various  processes  the  ovule 
has  become  a  mature  seed. 

The  changes  just  described,  together  with  some  others 
that  chiefly  affect  the  ovary,  take  place  whether  pollen 
from  the  same  flower  or  from  another  flower  of  the  same 


THE   FLOWER.  85 

species  is  applied  to  the  stigma;  but  it  has  been  proved 
that,  as  a  general  rule,  there  are  great  advaii- 

•  ,  ,      J  Pollination, 

tages  in  having  the  pollen  brought  from  another 
flower.1     Accordingly,  while  self-fertilization  is  possible  in 
most  plants,  various  arrangements  exist  by  which  cross- 
fertilization  is  favored. 

A  number  of  external  agents  serve  as  efficient  means  of 
pollination.     The  wind  carries  the  light  pollen  of 'pine  and 
other  trees  to  great  distances,  sometimes  even   External 
hundreds  of   miles,  insects    of   many  different  agents, 
kinds  are  actively  engaged  in  carrying  pollen  from  one 
flower  to  another,  and  humming  birds  visit  a  considerable 
number  of  species.     In  comparatively  few  cases  pollen  is 
conveyed  to  the  stigma  by  the  agency  of  water. 

Flowers  themselves  show  many  remarkable  adaptations 
that  favor  cross-fertilization.    The  most  important  of  these, 
as  discussed  at   length   by  Darwin   and   other  Adaptations 
writers,  are  the  following:  of  flowers, 

1.  Diclinism,  or  the  separation  of  stamens  and  pistils. 
These  are  borne  in  different  flowers,  either  on  the  same 
plant,  as  in  the  hazel,  oak,  etc.,  or  on  different  individuals, 
as  in  the  willows  and  poplars.  In  some  families,  as  the 
maples,  both  conditions  prevail.  Plants  with  staminate 
and  pistillate  flowers  on  the  same  individual  are  said  to 
be  monoecious,  those  in  which  the  separated  flowers  are 
on  different  individuals  are  dioecious,  and  those  in  which 
either  condition  exists  together  with  the  production  of 
some  perfect  flowers  are  called  polygamous.  Of  those  in 
which  the  separation  is  most  complete,  namely,  perfectly 
dioecious  species,  Darwin  says,  "  About  the  origin  of  such 

1  Cf .  Darwin,  Cross-  and  Self-fertilization  in  the  Vegetable  Kingdom  ; 
Miiller,  Fertilization  of  Flowers. 


86  STUDY   OF   COMMON    PLANTS. 

plants  nothing  is  known."  1     This  arrangement  practically 
necessitates  cross-fertilization. 

2.  Dichogamy,  or  the  maturing   of   stamens  before  or 
after  the  period  of  receptivity  of  the  stigma.     When  the 
stamens  shed  their  pollen  before  the  stigma  is  receptive, 
the  dichogamy  is  proterandrous ;  if,  on  the  other  hand,  the 
stigma  is  receptive  before  the  pollen  is  shed,  it  is  proter- 
ogynous..    The  former  condition  is  far  more  common  than 
the  latter.2 

3.  Prepotency  of   pollen    from    other  flowers.     It   has 
been  found  by  experiment  that  pollen  from  another  indi- 
vidual is  often  decidedly  prepotent  over  that  produced  by 
the  same  flower.     This  is  best  shown  by  placing  its  own 
pollen  on  the  stigma  of  a  flower,  and  after  some  hours 
applying  pollen  of  a  different  colored  variety  of  the  same 
species.     The   plants,  raised   from  seeds   of   flowers  thus 
fertilized   show   by   the    color    of    their   flowers    whether 
crossing  has  taken  place.     Darwin  found  in  a  number  of 
cases  that  pollen  of  another  individual  was  prepotent  after 
twenty-three  or  twenty-four  hours.3 

4.  Heteromorphism.     A  considerable  number  of  species 
produce  flowers  of  different  forms.     In  various  species  of 
Primula  and  Houstonia,  certain  individuals  have  long  sta- 
mens and  short  styles,  while  others  have  long  styles  and 
short  stamens.    Such  flowers  are  said  to  be  dimorphic,  while 
those    of   loosestrife,  Lytlirum  Salicaria,  L.,  which   have 
stamens  and  styles  of  three  different  lengths,  are  trimor- 
phic.     Both   conditions   involve    the    same  principle  and 
favor  cross-fertilization  in  a  remarkable  way.4 

1  Different  Forms  of  Flowers  on  Plants  of  the  Same  Species,  p.  278. 

2  Cf.  Gray,  Structural  Botamj,  p.  219,  et  seq. 
8  Cross-  and  Self-fertilization,  pp.  395,  396. 

4  Cf.   Darwin,  Different  Forms  of  Flowers   on  Plants  of  the    Same 
Species. 


THE  FLOWER.  87 

5.  Special  mechanisms.  Such  peculiarly  shaped  flowers 
as  those  of  the  lupine,  sage,  lady's-slipper,  milkweed,  and 
many  other  plants  exhibit  special  contrivances,  often  in 
the  form  of  an  exquisitely  arranged  mechanism,  by  which 
the  flower  is  adapted  to  some  particular  visitor  or  class  of 
visitors,  through  whose  agency  it  is  fertilized.  These  are 
described  at  length  in  various  works,  and  we  shall  have 
occasion  to  study  some  of  them  in  detail  as  we  take  up 
different  families  of  plants.1 

1  The  student  is  given  distinctly  to  understand  that  the  foregoing 
account  is  necessarily  incomplete,  and  must  be  supplemented  by  careful 
and  intelligent  reading  of  the  references  given,  if  even  a  fairly  complete 
comprehension  of  the  subject  is  to  be  attained.  It  is  by  no  means  the 
part  of  these  exercises,  with  their  brief  summaries,  to  cover  the  subject 
of  botany,  but  to  show  the  beginner  how  to  go  to  work. 


88  STUDY   OF   COMMON   PLANTS. 


VII.   FRUITS. 

MATERIAL   REQUIRED. 

Mature  fruits  of  sugar  maple.     Pods  of  common  locust. 

Capsules  of  opium  poppy  and  of  Llnaria  vulgaris,  Mill. 

Fruits  of  climbing  bitter-sweet,  Celastrus  scandens,  L.     Cranberries. 

A  miscellaneous  collection  of  fruits  from  the  market  and  elsewhere. 
Among1  the  most  easily  procurable  are  the  following :  Peanut, 
acorn,  common  plantain,  coriander,  colocynth,  milkweed,  black 
pepper,  juniper  berries,  raisins,  sumac  "berries,"  rose  hip,  fig, 
date,  banana,  star  anise,  cardamom,  cocoanut,  apple,  plum,  mul- 
berry, catalpa,  spiraea,  evening  primrose,  and  mullein. 

COMMON   LOCUST.     Robinia  Pseudacacia,  L. 

I.  Taking  dry,  unopened  specimens,  note  all  the  ex- 
ternal features,  as  form,  surface,  color,  and  texture.     Are 
there  any  remains  of  floral  structures  ? 

II.  Open  the  pod  and  draw  in  outline  the  inner  surface 
of  one  of  the  halves,  showing   the  position,  attachment, 
and  form  of  the  seeds.     Locate  the  funiculus  and  micropyle, 
and  indicate  their  position  by  letters  and  dotted  lines. 

III.  Describe  the  structure  and  mode  of  dehiscence  of 
the  fruit  and  classify  it.     How  many  carpels  are  there  ? 

POPPY.     Papaver  somniferum,  L. 
I.    With  uninjured  commercial  specimens  note 

1.  The  general  external  characters. 

2.  The  peculiar  stigma.    Count  the  number  of  divisions. 

3.  Mode  of  dehiscence. 


FRUITS.  89 

II.   Make  a  transverse  section  and  examine  the  internal 
structure.     Ascertain 

1.  Where  the  seeds  are  attached. 

2.  Number  and  position  of  the  placentae. 

3.  Number  of  carpels. 

SUGAR   MAPLE.     Acer  saccharinum,  Wang. 

I.    Taking  dried  specimens,  gathered  the  preceding  fall, 
notice 

1.  The  form  of  the  wings. 

o 

2.  Their  size  as  compared  with  the  rest  of  the  fruit. 

3.  The  lightness  and  strength  of  the  whole  structure. 

What  do  you  infer  as  to  the  mode  of   dissemi- 
nation ? 

II.  Make  an  outline  sketch  of  one  of  the  two  halves, 
mericarps,  into  which  the  fruit  separates. 

III.  Soak  some   of  the   fruits  in  water,  and  after  an 
hour  notice  what   changes   have   taken   place.      With  a 
sharp  knife  or  scalpel  remove  the  pericarp.     How  does  its 
outer  part  differ  from  the  inner  in  texture?     Has  the  seed 
become  wet?     Describe  the  means  of  protection  of  the 
embryo. 

IV.  Taking  a  mericarp  that  has  soaked  a  longer  time, 
or  better,  one   that  has  lain  on  the  moist  ground  from 
the  time  of  its  fall,  remove  the  pericarp  so  as  to  expose 
the  seed  in  its  natural  position.    Next  remove  carefully  the 
seed-coats  and  examine  the  embryo.     Observe  the  way  it 
is  folded  together  and  the  form  of  the  radicle  and  coty- 
ledons. 

V.  Classify  the  fruit.1 

1  Cf.  Goebel,    Outlines  of  Classification  and  Special  Morphology,  p. 
428 ;  Gray,  Structural  Botany,  Chap.  VII. 


90  STUDY   OF    COMMON   PLANTSo 

BUTTER- AND-EGGS.     Linaria  vulgaris,  Mill. 

I.  Place  some  of  the  dry  capsules  in  water  and  watch 
them  for  a  few  minutes.     Observe  and  record  any  changes 
that  take  place. 

II.  Ascertain  the  following  facts : 

1.  Number  of  carpels. 

2.  Position  of  placentae. 

3.  Mode  of  dehiscence. 

CLIMBING  BITTER-SWEET.     Celastrus  scandens,  L. 

I.  Examine  the  dry  fruits,  noting  the  number,  shape, 
and  position  of  the  reflexed  valves. 

II.  Compare  specimens  that  have  been  soaked  in  water 
an  hour  or  more  and  note  differences. 

III.  Ascertain  the  number  of  seeds  and  describe  them. 
They  are  surrounded  by  a  brightly  colored  aril.1 

IV.  Classify    the    fruit    and    describe    the    mode    of 
dehiscence. 

CRANBERRY.      Vaccinium  macrocarpon,  Ait. 

I.  Note  critically  the  external   features,  including  the 
presence  or  absence  of  floral  envelopes.     Can  you  deter- 
mine by  inspection  of  the  fruit  whether  the  ovary  should 
be  described  as  superior  or  inferior? 

II.  Prepare  transverse  and  longitudinal  sections.     De- 
termine 

1.  The  number  of  carpels. 

2.  Position  and  direction  of  seeds.     Draw  and  describe, 

1  Cf.  Gray,  Structural  Botany,  pp.  308,  309. 


FKUITS.  91 


CLASSIFICATION    OP   FRUITS. 

After  a  thorough  study  of  a  few  such  fruits  as  the  fore- 
going, examine  and  classify  a  large  number  of  easily  pro- 
curable sorts,  selected  so  as  to  secure  as  great  a  variety  as 
possible.  See  list  given  above.  Careful  attention  should 
be  given  at  the  same  time  to  their  morphology.  Endeavor 
to  ascertain  in  each  case  how  many  carpels  there  are,  and 
what  modifications  the  parts  forming  the  fruit  have  under- 
gone. It  is  desirable  to  adopt  some  one  classification  and 
adhere  to  it.  That  of  Gray  is,  on  the  whole,  the  most 
satisfactory. 

SPECIAL   STUDIES.1 

I.  Projection  of  seeds. 

II.  Arrangements  for  burying  seeds. 

III.  Colors  of  fruits. 

IV.  Relationships  indicated  by  fruits. 

V.    Variation  as  seen  in  cultivated  fruits. 
VI.    Minute  anatomy  of  the  cherry. 

VII.   Development  of  the  apple  or  some  other  common 
fruit. 

This  last  may  be  made  an  extremely  interesting  and 
profitable  study.  Beginning  with  the  flower  of  the  apple, 
cherry,  or  any  of  the  common  fruits,  watch  day  by  day  the 
changes  that  take  place,  keeping  a  full  record  of  them 
until  the  fruit  is  formed. 

1  Botanical  Gazette,  Vol.  VII  (1882),  pp.  125,  137  ;  Vol.  XII  (1887), 
p.  225  ;  Lubbock,  Flowers,  Fruits,  and  Leaves,  Chap.  Ill ;  Wallace,  Dar- 
winism, pp.  305-308  ;  Darwin,  Animals  and  Plants  under  Domestication, 
Vol.  I,  Chap.  XI ;  Strasburger  and  Hillhouse,  Practical  Botany,  p. 
347  et  seq. 


92  STUDY   OF   COMMON   PLANTS. 


REVIEW   AND    SUMMARY. 

After  the  process  of  fertilization  has  taken  place,  re- 
markable changes  occur  aside  from  those  of  the  ovule 
Development  already  described.  The  corolla  withers,  and 
of  the  fruit,  the  ovary  increases  in  size,  finally  becoming  the 
fruit,  which  in  ordinary  cases  is  to  be  thought  of  simply  as 
the  ripened  ovary.  In  some  species,  however,  the  calyx- 
tube  forms  a  part  of  the  fruit,  and  still  other  exceptional 
forms  of  developmental  history  occur.  The  wall  of  the 
ovary,  which  becomes  the'  pericarp,  generally  changes  in 
texture,  becoming  firm  and  leathery  as  in  the  bean,  or 
fleshy  as  in  the  cucumber,  or  partly  fleshy  and  partly  bony 
as  in  the  cherry,  and  so  on.  The  pericarp  often  shows 
three  fairly  distinct  layers  corresponding  to  the  upper  and 
lower  epidermis  and  intervening  parenchyma  of  the  car- 
pellary  leaf,  the  outer  layer  being  known  as  the  exocarp, 
the  middle,  mesocarp,  and  the  inner,  endocarp.  Thus,  in 
the  peach,  the  skin  is  the  exocarp,  the  fleshy  part  the 
mesocarp,  and  the  stone  the  endocarp.  In  the  pod  of  a 
bean  or  pea,  the  correspondence  between  the  parts  of  the 
pericarp  and  those  of  the  carpellary  leaf  is  still  more 
manifest.  In  many  other  fruits  the  changes  that  have 
occurred  render  this  relation  less  easily  observed,  and  are 
frequently  still  more  fundamental  in  character.  In  some 
cases  in  which  the  ovary  is  composed  of  several  carpels, 
only  one  develops,  the  rest  becoming  abortive ;  in  others 
the  ovary  becomes  divided  by  one  or  more  septa,  which 
give  the  fruit  the  appearance  of  having  arisen  from  a  com- 
pound pistil  with  more  than  the  actual  number  of  carpels. 
These  and  other  important  features  of  the  developmental 
history  of  fruits  are  best  understood  by  a  careful  com- 
parison of  their  structure  in  different  stages  of  growth 
from  the  pistil  to  the  mature  condition. 


FEUITS.  93 

Many  of  the  peculiarities  just  referred  to  find  their  expla- 
nation in  physiological  adaptations,  chiefly  those  connected 
with  protection  and  the  dissemination  of  seeds,  physiological 
Attention  has  already  been  directed  to  these  in  adaptations, 
our  study  of  seeds,  but  they  may  now  be  briefly  noticed 
with  more  direct  reference  to  the  fruit.  Fleshy  fruits,  par- 
ticularly if  brightly  colored,  are  attractive  to  animals,  and 
are  carried  away  by  them  in  great  numbers,  often  to  very 
remote  places.  One  has  only  to  recall  the  habits  of  birds 
in  distributing  seeds  of  cherries,  strawberries,  and  many 
other  fruits,  to  realize  the  importance  of  these  common  and 
familiar  but  nicely  adjusted  relations.  Other  fruits,  such 
as  nuts  of  various  kinds,  though  less  attractive  externally, 
are  carried  away  by  squirrels  and  other  animals  for  the 
sake  of  the  abundant  food  stored  up  in  them.  Still  other 
fruits,  such  as  the  samara  of  the  hop-tree  and  maple,  have 
the  pericarp  greatly  modified  in  adaptation  to  dissemina- 
tion by  the  wind,  and  a  considerable  number  of  dehiscent 
fruits  exhibit  mechanical  arrangements  by  which  their 
seeds  are  forcibly  thrown  to  a  considerable  distance.  Fre- 
quently, too,  the  structure  of  the  fruit  is  manifestly 
adapted  to  secure  the  protection  of  the  seed.  The  thick 
and  bitter  outer  covering  of  the  walnut  and  its  extremely 
hard  shell,  the  rind  of  the  orange  with  its  pungent, 
aromatic  oil,  the  extraordinarily  multiplied  and  thickened 
coverings  of  the  cocoanut,  and  other  arrangements  of  simi- 
lar character,  are  so  many  means  of  protection  against 
attacks  of  animals,  the  penetration  of  water  and  fungous 
germs,  and  injury  from  other  destructive  agents. 

In  systematic  botany  it  becomes  necessary,  for 'the  sake 
of  intelligible  description,  to  employ  some  one  of  the 
various  classifications  of  fruits.  At  the  same  time,  it  must 
be  understood  that  such  classifications  are  more  or  less 


94  STUDY   OF   COMMON   PLANTS. 

artificial,  and  that  their  value  is  rather  that  of  convenience 
than  as  an  expression  of  relationship.  Nevertheless  it  is 
Classification,  the  case  many  times  that  in  a  given  group  of 
Mkated^by  plants  a  certain  kind  of  fruit  prevails,  not  in- 
fruits,  frequently  to  the  exclusion  of  all  other  kinds. 

Thus  the  pepo  is  the  fruit  of  the  gourd  family,  the  ache- 
mum  of  the  composites,  and  so  on,  so  that  by  means  of  the 
fruit  alone  it  is  often  possible  to  determine  the  relation- 
ship of  the  plant  from  which  it  came.  Accordingly  the 
student  is  advised  to  familiarize  himself  with  the  various 
kinds  of  fruits  by  a  careful  study  and  classification  of  such 
a  collection  as  that  of  the  list  in  this  exercise,  and  in  his 
subsequent  study  of  special  groups  of  plants  to  observe 
how  far  the  kind  of  fruit  is  characteristic.  Such  a  mode  of 
procedure  will  give  interest  and  meaning  to  what  other- 
wise is  likely  to  be  nothing  more  than  a  bete  noire  to  the 
beginner. 

In  closing  our  study  of  fruits  we  come  back  again  to  the 
seed,  with  which  we  started,  and  it  must  already  have  oc- 
Cycle  of  de-  curred  to  those  who  are  in  the  habit  of  stopping 
flowering*  °  to  think,  that  the  same  plant  appears  at  differ- 
piants.  eiit  periods  of  its  life  under  widely  different 

forms.  The  seed  represents  the  plant  in  its  period  of  rest, 
but  it  is  as  truly  the  plant  in  this  state  as  in  its  period  of 
highest  activity.  We  may  even  hold,  perhaps  more  accu- 
rately, that  a  part  of  the  seed — the  embryo  —  strictly  rep- 
resents the  entire  plant,  the  parts  around  the  embryo  being 
merely  protective  or  food-supplying  accessories  that  belong 
in  reality  to  the  preceding  generation.1  We  have  found  it 
best  to  study  parts  of  many  different  species  in  order  to 

1  The  theory  of  the  alternation  of  generations  and  the  details  of 
the  reproductive  process  cannot  well  be  discussed  until  the  student  is 
acquainted  with  flowerless  plants. 


FRUITS.  95 

obtain  a  general  conception  of  the  structure  and  cycle  of 
development  of  flowering  plants,  but  if  we  were  to  take  a 
single  seed,  and  watch  its  germination  and  every  detail  of 
its  subsequent  life  and  growth,  we  should  find  its  develop- 
mental history  a  connected  synopsis  of  what  we  have 
learned  from  so  many  sources.  This  may  be  stated  briefly 
as  follows:  In  the  spermaphytes,  or  higher  plants,  the 
embryo  arises  from  a  single  cell,  the  ob'sphere,  contained 
in  the  embryo-sac.  The  embryo  has  all  the  essential  vege- 
tative parts  of  the  mature  plant,  and  in  germination  these 
are  unfolded,  finally  developing  into  root,  stem,  and  leaf. 
Certain  buds  of  the  plant  in  this  later  stage  of  its  develop- 
ment become  ordinary  branches,  while  others  undergo  ex- 
traordinary modifications  and  become  reproductive  branches 
or  flowers.  In  due  course  of  time  the  oosphere  is  formed 
in  the  embryo-sac  of  the  various  ovules,  and  after  fertiliza- 
tion the  same  history  is  repeated  in  a  subsequent  genera- 
tion. Later  on  in  our  work  we  shall  see  that  plants  lower 
in  the  scale  of  life  exhibit  similar,  though  not  identical, 
phases  of  developmental  history.  Before  proceeding  to 
these,  however,  we  have  first  to  study  certain  relationships 
of  the  higher  plants  among  themselves. 


96  STUDY  OF   COMMON    PLANTS. 


VIII.     SEAWEEDS  AND  THEIR  ALLIES.    ALG^B. 

MATERIAL  REQUIRED. 

Green  algse  gathered  in  a  fresh  condition  from  different  places. 
Pains  should  be  taken  to  secure  the  coarser,  branching  sorts, 
common  in  running  water,  the  fine,  silky  kinds  that  grow  abun- 
dantly in  stagnant  water,  and  the  dull  green  felt  that  forms 
on  the  damp  ground  and  in  pots  in  conservatories. 

NOTE  TO  THE  TEACHER.  —  The  arrangement  of  families  and  higher 
groups  in  the  following  pages  is  believed  to  indicate,  as  well  as  a  lineal 
arrangement  can,  their  natural  succession,  and  is  that  adopted  by  modern 
botanical  writers.  In  most  preparatory  schools,  however,  certainly  in 
those  not  fully  equipped  for  microscopic  work,  the  best  results  will  be 
attained  by  following  a  somewhat  different  order.  After  studying  the 
organs  of  flowering  plants,  it  will  be  found  advantageous  to  pass  at  once 
to  the  Coniferae,  then  to  the  early  flowering  families  of  phanerogams, 
taking  them  in  the  order  that  is  most  convenient,  which  will  be  deter- 
mined chiefly  by  time  of  flowering  and  abundance  of  material.  As  a  rule, 
the  cryptogams  should  be  studied  later,  although  in  schools  provided  with 
a  full  laboratory  outfit  the  order  followed  in  the  book  may  be  the  best. 

No  attempt  is  made  to  treat  all  families  alike.  The  aim  is  simply  to 
help  the  student  in  every  case  to  ascertain  existing  facts  and  their  mean- 
ing. Observation  should  constantly  be  directed  to  the  differences  and 
resemblances  by  which  various  degrees  of  relationship  are  determined. 
The  exercises  on  the  Coniferse  and  Ranunculacese  will  serve  to  indicate 
the  prominence  that  may  properly  be  given  to  this  idea,  which  forms  the 
basis  of  vegetable  morphology.  On  the  other  hand,  observations  of 
distribution  and  physiological  adaptations,  too  much  neglected  hitherto, 
should  receive  their  full  share  of  attention.  It  is  essential  that  careful 
descriptions  of  the  plants  examined  should  be  written,  and  that  these 
should  be  accompanied  by  sketches.  The  number  of  these  will  vary 
according  to  circumstances  and  the  judgment  of  the  teacher,  but  they 
are  by  no  means  to  be  omitted. 


SEAWEEDS    AND   THEIK    ALLIES.  97 

SPIROGYRA.     S.  longata,  qulnina,  etc. 

General  Characters. 

The  soft,  green  material  called  "  pond  scum,"  growing 
on  the  surface  of  still  water,  is  usually  made  up  largely 
of  Spirogyra,  not  infrequently  several  species  together. 
Notice 

I.  The  color,  varying  according  to  conditions,  so  that 
specimens  from  different  places,  or  gathered  at  different 
times  of  year,  may  present  a  wide  range  of  shades. 

II.  The  delicate  and  slippery  feeling,  reminding  one  of 
silk  when  taken  between  the  fingers. 

III.  The  remarkable  difference  in  size  of  the  filaments 
when  examined  with  a  hand  lens,  or  even  with  the  naked 
eye,  if  specimens  of  extreme  sizes  are  compared. 

Microscopic  Structure. 

Mount  in  water  and  examine  with  the  compound  micro- 
scope. 

I.  Observe  that  each  filament  is  composed  of  a  single 
row  of  cells.     Follow  one   of  the  filaments  to  the  end. 
Are   the   cells   composing   it   of   uniform   diameter?      Of 
uniform  length  ?     How  does  the  terminal  cell  differ  from 
the  others? 

II.  Study  critically  the  cell  structure. 

1.  Focus  slowly  and  compare   one    cell   with   another 

until  you  are  satisfied  as  to  their  geometrical  form. 
Are  they  "  rectangular  "  or  cylindrical  ? 

2.  Separate  the  cell-contents  from   the   cell-membrane 

by  applying  a  plasmolyzing  agent.     Two  per  cent 


98  STUDY   OF   COMMON   PLANTS. 

salt  solution  is  suitable  for  this  purpose.  Watch 
the  process  of  plasmolysis  (contraction  of  the  proto- 
plasm and  its  separation  -from  the  cell-membrane) . 
Sketch  one  or  two  of  the  cells  showing  the  cell- 
membrane  in  its  place  and  the  contracted  proto- 
plasmic contents. 

3.  Preparing  a  fresh  slide,  so  as  to  have  the  cells  in 

their  natural  condition,  study  the  cell-contents. 
How  many  green  bands,  chlorophyll  bodies,  are 
there  in  each  cell?  Change  the  focus  slowly,  and 
follow  a  band  from  one  end  of  the  cell  to  the 
other.  What  is  its  shape?  Is  its  edge  even  or 
irregular?  Notice  the  rounded,  highly  refractive 
bodies,  pyrenoids,  contained  in  it. 

4.  Treat  with  iodine  solution,    and  ascertain  whether 

starch  occurs  in  the  cells.  If  so,  does  it  stand 
in  any  relation  to  the  pyrenoids  ? 

5.  Look  for  a  nucleus.     This  is  sometimes  brought  out 

very  plainly  by  the  action  of  iodine.  In  some 
species  it  may  be  seen  with  perfect  clearness  with- 
out any  treatment.  Compare  different  specimens 
until  you  know  definitely 

a.  The  position  of  the  nucleus  in  the  cell. 

b.  Its  shape. 

c.  Whether  it  is  connected  in  any  way  with  other 

parts  of  the  protoplasmic  contents.  This  is  a 
very  interesting  point,  difficult  to  determine  in 
some  species,  but  very  obvious  in  others. 

d.  Its  structure.     A  nucleolus   will  readily  be  found. 

(The  finer  details  of  structure  require  special 
methods  not  provided  for  in  this  course.) 


SEAWEEDS   AND  THEIR   ALLIES.  99 

III.  Draw  one  of  the  cells  with  great  care  large  enough 
to  show  its  complete  structure.  This  will  require  close 
attention  to  details.  Repeat,  if  necessary,  until  you  are 
satisfied  that  your  drawing  represents  truthfully  a  Spiro- 
gyra  cell. 

Describe  fully  what  you  have  seen  so  far. 

NOTE.  —  Possibly  some  things  have  escaped  notice.  The  septa  between 
adjacent  cells  differ  widely  in  different  species.  There  are  still  other 
points  not  likely  to  be  observed  except  by  comparing  different  forms. 

Reproduction. 

Spirogyra  is  reproduced  sexually  by  zygospores  and  non- 
sexually  by  cell-division. 

I.  By  zygospores.  These  may  be  found  in  the  summer 
time  in  specimens  that  look  faded  or  discolored.  They 
are  not  to  be  looked  for  in  bright  green  material. 

1.  Observe  the  marked  contrast  presented  by  the  conju- 

gating filaments  to  those  in  the  vegetative  condition. 
The  filaments  occur  in  pairs,  one  with  empty  cells, 
the  other  containing  in  each  of  its  cells  a  large, 
commonly  oval  zygospore. 

2.  Notice  the  structure  of  the  zygospore,  with  its  heavy 

wall  and  dense  contents. 

3.  Compare  different  specimens,  and  try  to  make  out  the 

way  in  which  the  zygospores  have  been  produced. 
Notice  the  connecting-tube  by  which  the  cells  of 
the  empty  filament  are  connected  with  those  of  the 
one  containing  zygospores.  See  if  there  are  any 
cases  in  which  it  contains  protoplasm.  Look  for 
specimens  in  which  instead  of  a  complete  tube  there 
are  protuberances  from  the  opposite  cells  of  the 


100  STUDY  OF  COMMON  PLANTS. 

two  filaments.  If  the  material  is  favorable,  you 
will  be  able  by  continuing  such  a  comparison  to 
observe  for  yourself  the  successive  stages  in  the 
development  of  the  zygospores.1 

II.  By  cell-division.  The  nucleus  undergoes  a  remark- 
able series  of  changes,  ending  in  its  separating  into  two 
new  nuclei  and  the  formation  of  a  septum  between  them. 
In  this  way  a  cell  becomes  divided  into  two  "daughter 
cells  "  which  after  attaining  their  full  development  divide 
in  the  same  way,  the  process  continuing  through  a  series  of 
generations.2 

Spirogyra  is  one  of  the  most  abundant  and  widely 
distributed  of  the  green  algae.  It  is  always  to  be  had,  and 
is  one  of  the  most  satisfactory  plants  with  which  to  begin 
the  study  of  the  plant  cell.  Zj^gnema,  recognized  by  its 
stellate  chlorophyll  bodies,  and  Mesocarpus,  in  which  a  flat 
plate  takes  the  place  of  a  spiral  band,  are  both  often  found 
with  it.  All  of  these,  particularly  Spirogyra  and  Meso- 
carpus, are  capable  of  almost  unlimited  use  in  the  demon- 
stration of  fundamental  facts  of  vegetable  physiology. 
The  student  will  do  well  to  read  carefully  what  is  said 
of  Spirogyra  in  the  laboratory  manuals,  and  consult  the 
references  in  Arthur,  Barnes,  and  Coulter's  Plant  Dissec- 
tion, and  the  recent  periodical  literature. 

1  Cf.  Strasburger,   Practical   Botany,  p.  247 ;    Sachs,  Physiology   o> 
Plants,  pp.  727,  728. 

2  For  details  of  the  process,  including  nuclear  changes,  see  Strasburger' s 
admirable  monograph,  Ueber  Kern-  und  Zelltheilung.    Jena,  1888. 


SEAWEEDS   AND   THEIR   ALLIES,  i        ^     1   J, 


VAUCHERIA.      V.  sessilis,  Yauch: '  ' 
General  Characters. 

Examine  with  a  good  hand  lens  the  specimens  that 
have  been  gathered,  some  from  fresh  water,  others  from 
moist  soil  in  greenhouses.  Notice 

I.  The  coarsely  filamentous  appearance,  and  the  matting 
together  to  form  a  thick  felt,  when  growing  on  the  soil  in 
flower-pots. 

II.  The  color.     Compare  with  the  bright  green  of  some 
of  the  finely  filamentous  sorts  growing  in  water. 

Microscopic  Structure. 

Mount  some  of  the  filaments  and  examine  with  the 
compound  microscope.  Observe 

I.  The  very  large  size  of  the  cells,  a  filament,  as  a  rule, 
consisting  of  a  single  cell.     Try  to  find  the  end  of  one. 
Ascertain  whether  branches  are  formed. 

II.  The  thick  cell-wall.     Run  two  per  cent  salt  solution 
under  the  cover  glass,  and  see  if  the  wall  becomes  more 
plainly  defined. 

III.  The  cell-contents.     These  present  considerable  dif- 
ferences, depending  on  the  age  of  the  plant,  and  the  con- 
ditions under  which  it  grew.     Good  specimens  show  in 
the  thicker  protoplasm  next  to  the  cell- wall 

1.  Chlorophyll  bodies.     Observe  their  shape. 

2.  Drops  of  oil.     Apply  iodine  solution,  and  determine 

whether  starch  also  is  present. 

3.  Nuclei.    These  require  special  treatment  to  be  brought 

out  satisfactorily.1 

1  Cf.  Bower  and  Vines,  Practical  Botany,  II,  p.  76. 


102  STUDY   OF   COMMON    PLANTS. 


Vaucheria  is  reproduced  by  oospores  and  also  by  swarm- 
spores.1 

I.  By  oospores.  These  are  easily  obtained  from  speci- 
mens growing  on  damp  earth,  and  may  be  satisfactorily 
studied  both  in  living  and  alcoholic  material.  Using  first 
the  low  power  of  the  compound  microscope,  observe 

1.  The  organs  of  reproduction  generally  growing  close 

together. 

a.  The  cylindrical  anther  idium. 

b.  The  obliquely  oval  oogonia,  commonly  two  with 

each  antheridium.     Draw. 

2.  The  structure  of  both  antheridium  and  oogonium. 

Examine  this  more  in  detail,  using  the  high  power, 
and,  if  practicable,  having  fresh  material. 

a.  Early  stages  of  development  may  be  found.      If 

these  are  met  with,  make  a  series  of  sketches, 
showing  both  oogonia  and  antheridia  at  dif- 
ferent periods. 

b.  The  process  of  fertilization  should  be  observed,  if 

possible.  It  will  probably  involve  the  outlay 
of  considerable  time,  yet  there  are  few  plants 
in  which  the  process  can  be  more  satisfactorily 
followed.  It  is  even  more  striking  in  CEdogo- 
nium,  a  plant  closely  related  to  Vaucheria,  on 
account  of  the  large  size  of  the  antherozoids.2 

II.  By  swarm-spores.  These  cannot  always  be  had 
when  wanted,  but  are  unusually  large,  and  on  account  of 

1  For  other  forms  of  vegetative  reproduction,  cf.  Goebel,  Outlines  of 
Classification  and  Special  Morphology,  p.  32. 

2  For  an  account  of  the  process  and  further  directions,  cf.  Strasburger, 
Practical  Botany,  pp.  252-254. 


SEAWEEDS   AND  THEIE   ALLIES.  103 

their  peculiarities  are  worth  taking  pains  to  secure.  Stras- 
burger  recommends 1  that  vigorous  specimens  of  Vaucheria, 
growing  in  running  water,  be  obtained  the  day  before, 
placed  in  shallow  vessels,  and  fresh  water  poured  over 
them.  The  swarm-spores  are  formed  the  following  morn- 
ing, and,  on  account  of  their  large  size,  both  their  structure 
and  development  are  readily  observed. 

No  further  special  directions  will  be  needed  beyond 
those  in  the  manuals  referred  to,  which  should  be  care- 
fully read.  As  complete  a  study  as  possible  should  be 
made  of  this  plant,  since  it  stands  as  a  representative  of 
those  algse  in  which  the  sexual  reproduction  has  proceeded 
a  step  farther  than  in  Spirogyra,  male  and  female  cells 
being  distinctly  differentiated.  Many  of  these  are  also 
reproduced  by  swarm-spores.  These  two  modes  of  repro- 
duction are  so  common  that  we  expect,  as  a  general  rule, 
to  find  the  algae  reproducing  themselves  both  sexually  and 
non-sexually,  a  fact  that  continually  presents  itself  in 
studying  other  groups  of  plants,  but  not  often  in  quite  so 
striking  a  way  as  here.  The  non-sexual  process  is  a  means 
of  rapid  reproduction  ;  sexual  reproduction,  on  the  other 
hand,  commonly  results,  in  the  lower  plants  at  least,  in  the 
formation  of  a  resting-spore  by  which  the  plant  is  carried 
through  various  vicissitudes  and  dangers,  and  in  which 
by  a  mingling  of  the  male  and  female  elements  in  the 
process  of  fertilization,  certain  other  advantages,  not  yet 
fully  understood,  are  attained. 

The  brown  and  red  algae  grow  in  salt  water  in  nearly  all 
cases,  and  are  seaweeds  properly  so  called.  They  present 
many  forms  no  less  interesting  than  the  green  algae,  but  as 
they  will  not  be  accessible  to  the  great  majority  of  those 

1  Practical  Botany,  p.  250.  See  also  Bower  and  Vines,  Practical 
Botany,  II,  pp.  78-80. 


104  STUDY   OF  COMMON   PLANTS. 

who  are  likely  to  use  this  book  their  study  has  not  been 
introduced.  The  various  text-books  and  manuals  give  the 
necessary  help  for  beginning  their  study.1 

1  No  provision  is  made  in  this  work  for  the  study  of  fungi,  not  because 
they  are  unimportant,  but  because  it  is  better  on  the  whole  that  the 
student  should  complete  his  preparatory  course  with  the  definite  under- 
standing that  he  knows  nothing  whatever  about  this  vast  and  hetero- 
geneous group. 


MOSSES   AND  LIVERWORTS.  105 


IX.   MOSSES   AND   LIVERWORTS. 

MATERIAL  REQUIRED. 

A  collection  of  common  mosses  of  different  genera,  e.g.  Bryum, 
Climacium,  Mnium,  Polytrichum,  Cylindrothecium,  Sphagnum, 
and  others.  AVith  care  in  selecting,  and  by  gathering  material 
at  different  times,  some  specimens  will  be  obtained  in  fruit, 
others  in  the  vegetative  condition,  and  still  others  with  arche- 
gonia  and  antheridia. 

A  similar  collection  of  liverworts,  including  representatives  of  the 
genera  Conocephalus,  Lunularia,  Riccia,  Porella,  etc. 

MOSSES.     Musci. 
General  Characters. 

Without  selecting  one  species  for  exclusive  study,  com- 
pare the  different  kinds  of  mosses  in  the  collection  that 
has  been  made,  and  ascertain  what  general  characters  they 
have  in  common.  Notice 

I.  Their  choice  of   locality.     By  what  does  it  appear 
to  be  determined?     Are  the  habits  of  the  different  species 
alike  in  this  respect? 

II.  Whether  they  grow  separately  or  in  tufts. 

III.  The  differentiation  of  vegetative  organs.     Is  there 
a  plain  distinction  of  root,  stem,  and  leaf?     If  so,  is  it 
equally  marked  in  the  different  species  ? 

IV.  Differences  of  size,  color,  and  other  specific  char- 
acters. 


106  STUDY   OF   COMMON   PLANTS. 

V.  The  fructification,  —  when  fully  developed  a  very 
conspicuous  part  of  the  plant. 

Rhizoids. 

I.  Examine  the  different  species  with  reference  to  the 
occurrence   of  roots.     They  are  found  to  have  the  form 
of  hair-like  bodies,  root-hairs,  or  rhizoids.     Where  do  they 
arise  ?     Are  they  limited  to  any  one  part  of  the  plant  ? 

II.  Remove  some  of  the  rhizoids,  mount  in  the  usual 
way,  and  examine  under  the  compound  microscope.     Pre- 
pare several  slides,  taking  the  root-hairs  from    different 
species,  and  from   different  parts  of   the  same  plant  for 
comparison. 

1.  Notice  first  the  color,  mode  of  branching,  and  other 

external  features. 

2.  Study  more  closely  the  minute  structure,  observing 

the  form  of  the  cells  composing  the  rhizoids,  the 
character  of  their  contents,  and  position  of  the 
septa.1 

3.  Notice  whether  the  younger  cells   of   the   rhizoids 

differ  from  the  older  ones,  and  if  so  how.  Also 
whether  exposure  to  different  conditions,  as  a 
greater  or  less  amount  of  light,  has  any  effect  on 
the  character  of  the  cells  or  their  contents. 

Stem. 

I.  Compare  the  stems  of  the  different  mosses,  and  observe 
their  differences  of  size  and  habit,  contrasting  the  erect, 
rigid  stem  of  Climacium  with  the  delicate,  spreading 
branches  of  Mnium,  the  minute  forms  of  Barbula  with 
the  coarse  Polytrichum,  and  so  on. 

1  Cf.  Sachs,  Physiology  of  Plants,  p.  30. 


MOSSES   AND   LIVERWORTS.  107 

II.  Cut  thin  transverse  sections  of  the  stems  of  two 
or  three  different  species,  and  study  them  under  the  com- 
pound microscope.  Beginning  with  the  outside,  notice 

1.  The  epidermis,  consisting  of  a  single  layer  of  periph- 

eral cells.  Underneath  this,  in  some  of  the 
species,  are  similar,  thick-walled  cells,  the  whole 
forming  a  cylindrical  band  of  mechanical  tissue. 

2.  The  cortex,  consisting  of  rounded  cells,  often  con- 

taining starch  and  oil. 

3.  The  axial  cylinder,  an  extremely  simple  form  of  fibro- 

vascular  bundle,  occupying  the  center  of  the  stem, 
and  made  up  of  much  narrower  elements  than 
those  composing  the  cortex.  Longitudinal  sec- 
tions show  that  these  are  also  much  more  elongated 
than  the  cortical  cells  are.  Observe  also  whether 
they  differ  from  the  latter  in  the  color  of  their 
walls  and  the  character  of  their  contents. 

Leaf. 

I.  Examine  next  the  ordinary  foliage  leaves  of  the 
different  species,  observing 

1.  Their  differences  of  size,  form,  and  other  external 

features. 

2.  Their  relation  to  the   stem.     Are    they  stalked   or 

sessile?  Is  their  arrangement  on  the  stem  alike 
in  the  different  species  ? 

3.  The  structure   of  an   individual  leaf,  as  far  as  this 

can  be  observed  under  a  good  lens.  Notice  par- 
ticularly the  margins  and  midrib. 

II.  Study  fresh  and  well-developed  leaves,  such  as  those 
of  new  shoots  of  Mnium,  with  the  compound  microscope. 
The  cellular  structure  will  be  found  beautifully  distinct, 


108  STUDY   OF   COMMON    PLANTS. 

the  cells  containing  large  and  clearly  defined  chlorophyll 
bodies.  Notice  their  position  in  the  cells ;  does  it  appear 
to  be  constant? 

A  little  attention  will  show  that  the  leaf  is  not  a  simple 
plate  of  cells  throughout.  Examine  the  midrib  and  com- 
pare with  the  axial  cylinder  of  the  stem. 

III.  Look  for  other  kinds  of  leaves,  scale  leaves,  of 
frequent  occurrence,  especially  on  the  lower  part  of  the 
stem,  and  perichaetial  leaves,  forming  a  rosette,  usually  at 
the  apex  of  fruiting  stems.1 

Fructification. 

I.  Taking  any  of  the  mosses  in  the  collection  that  are 
in  fruit  —  several  species  if  possible  —  observe 

1.  The  slender  stalk,  seta,  on  which  is  borne 

2.  The  capsule,  containing  spores. 

Compare  the  capsules  of  different  species  as  to  size, 
form,  color,  and  other  features. 

II.  Make  a  thorough  study  of  the  parts  composing  the 
capsule,  using  the  compound  microscope  when  needed. 

1.  The  calyptra,  commonly  a  thin  membrane  covering 

the  apical  part  of  the  capsule ;  rarely,  as  in 
Polytrichum,  a  thick  hairy  cap.  Notice  the  form, 
differing  in  different  genera. 

2.  The  opercurum,  in  most  genera  a  conical  lid,  fitting 

closely  to  the  end  of  the  capsule,  but  thrown  off 
when  the  latter  is  fully  ripe,  thus  permitting  the 
scattering  of  the  spores. 

3.  Lightly  covered   by   the    operculum    when  it   is   in 

place,  but   showing   conspicuously  when  it  is  re- 

1  For  further  suggestions  cf.  Arthur,  Barnes,  and  Coulter,  Plant  .Dissec- 
tion, p.  84  et  seq. 


MOSSES   AND    LIVERWORTS.  109 

moved,  the  peristome,  or  circle  of  teeth  surround- 
ing the  opening  of  the  capsule.  The  peristome 
presents  a  widely  different  appearance  in  the 
different  genera,  and  its  structure  requires  careful 
study.  It  consists  of  four,  eight,  sixteen,  thirty- 
two,  or  sixty-four  teeth,  plain,  or  variously  cut  and 
ribbed,  and  often  very  hygroscopic.  In  a  few 
genera  the  peristome  is  wanting. 

4.  Within  the  capsule,  the  spores   filling  a  cylindrical 

space  which  surrounds  a  central  mass  of  tissue 
called  the  columella. 

5.  In  some  mosses,  besides  the  parts   already   named, 

there  are  to  be  observed  the  epiphragm,  a  thin, 
membranaceous   structure,   stretching    across   the 
mouth  of   the    capsule ;    and   at   the   base  of  the 
-capsule  a  swelling  called  the  apophysis. 

NOTE.  — The  structure  of  the  capsule  should  be  studied  in  detail 
in  a  number  of  different  mosses,  and  descriptions  accompanied 
by  careful  drawings  should  be  written.  The  peristome,  especially, 
is  very  characteristic  and  furnishes  important  features  for  the  sys- 
tematic study  of  the  group. 

Protoiiema. 

If  ripe  spores  are  sown  on  moist  soil,  or  on  a  compact 
clump  of  moss,  and  kept  under  a  bell-jar  at  the  temperature 
of  an  ordinary  living  room,  the  early  stages  of  develop- 
ment of  the  protonema  are  easily  observed.  The  spore 
swells  and  pushes  out  a  papilla  which  elongates  into  a 
tubular  cell.  This  increases  in  length,  becomes  septate,  and 
branches  are  formed. 

The  later  stages  of  development  may  be  followed  out 
with  the  same  material ;  but  there  are  some  advantages  in 
obtaining  vigorous  specimens  by  the  simple  expedient  of 
turning  a  clump  of  moss  bottom  side  up,  and  keeping  it  in 


110  STUDY    OF    COMMON    PLANTS. 

a  moist  atmosphere  for  a  week  or  two.  By  this  means  the 
relation  of  rhizoids  and  protonema  is  made  clear.  It  is 
seen  that  they  are  the  same  thing,  the  filamentous  growth 
taking  the  appearance  and  structure  of  protonema  or 
rhizoids  according  to  the  conditions  under  which  it  grows. 
It  is  also  seen  that  the  protonema  may  originate  from 
other  parts  of  the  plant,  as  well  as  from  the  spore. 

On  the  protonema,  whether  it  has  its  origin  in  the  spore, 
or  from  some  other  part  of  the  plant,  buds  arise,  from  which 
new  plants  are  formed. 

Archegoiiia  and  Antlieridia. 

Among  the  specimens,  if  these  have  been  gathered  at  dif- 
ferent times  of  year,  some  will  be  likely  to  show  "flowering 
heads,"  most  frequently  terminating  the  stem,  and  sur- 
rounded by  a  more  or  less  conspicuous  rosette  of  leaves, 
the  perichaetium.  The  antheridia  and  archegonia  may 
occur  together  in  the  same  "  flower,"  or  in  separate  flow- 
ers, on  the  same  or  on  different  individuals. 

The  whole  structure  is  best  studied  by  means  of  longi- 
tudinal sections,  which  are  easily  made  with  a  razor,  after 
a  little  practice,  without  any  previous  preparation  of  the 
specimen.  Examining  such  sections  under  the  microscope, 
if  we  chance  to  have  selected  a  male  specimen  we  shall 
find  antheridia  in  great  numbers  growing  at  the  apex  of 
the  axis,  and  with  them  slender,  filamentous  bodies,  para- 
physes,  while  outside  of  both  is  the  circle  of  perichsetial 
leaves.  The  antheridia  are  sacs,  usually  oblong  in  shape, 
with  a  wall  consisting  of  a  single  layer  of  cells,  the  interior 
being  composed  of  the  mother  cells  of  the  antherozoids. 
The  latter  are  ciliated,  protoplasmic  bodies,  closely  resem- 
bling those  of  the  ferns.  In  the  examination  of  a  female 
specimen  the  paraphyses  are  seen  as  before,  but  archegonia 


MOSSES   AND   LIVERWORTS.  Ill 

take  the  place  of  antheridia.  A  fully  formed  archegonium 
is  a  flask-shaped  body  with  an  elongated  neck,  and  an 
enlarged  ventral  portion,  within  which  is  the  oosphere. 

Fertilization  takes  place  by  the  mingling  of  the  substance 
of  an  antherozoid  with  that  of  the  oosphere,  after  the 
antherozoid  has  forced  it  way  down  through  the  long  canal 
of  the  neck.  The  fertilized  oosphere,  now  called  the 
oospore,  becomes  septate,  and  by  still  further  cell-division 
and  growth  the  capsule  with  its  seta,  spores,  and  various 
parts  already  described,  is  formed. 

With  suitable  material  and  sufficient  time  the  student 
can  readily  verify  most  of  the  facts  here  given. 

Cycle  of  Development. 

It  will  be  observed  that  in  the  mosses  alternation  of 
generations  takes  place.  The  sporophyte,  or  non-sexual 
generation,  begins  with  the  formation  of  the  oospore  and 
closes  with  the  spore,  while  the  oophyte,  or  sexual  genera- 
tion, begins  with  the  germination  of  the  spore,  and  includes 
both  protonema  and  leafy  plant. 

NOTE.  —  It  is  important  that  this  should  be  perfectly  clear.  The 
student  must  see  for  himself  the  various  stages  of  development  of  the 
mosses  as  far  as  this  is  practicable.  He  may  now  consult  the  various 
text-books  and  manuals,  particularly  those  of  Goebel,  Arthur,  Barnes, 
and  Coulter,  Bower  and  Vines,  and  the  references  given  by  them.  See 
further  on  this  subject  under  Ferns. 

t 

The  peat  mosses,  Sphagnacese,  are  easily  obtained  in 
many  parts  of  the  country,  and  afford  an  opportunity  for 
extended  and  profitable  comparative  study.  Their  habits, 
structure  of  the  vegetative  organs,  and  fructification,  all 
present  interesting  points  of  difference  from  the  true 
mosses. 


112  STUDY   OF  COMMON   PLANTS. 

LIVERWORTS.     Hepaticce. 

The  liverworts  are  closely  allied  to  the  mosses,  their 
cycle  of  development  being  essentially  identical  with  that 
of  the  latter  group.  Accordingly  our  work  will  be  re- 
stricted to  a  comparison  of  the  general  characters  of  some 
of  the  most  easily  procurable  liverworts.  Representatives 
of  the  genera  named  at  the  beginning  of  this  section  are 
widely  distributed  and  easily  obtained  through  a  con- 
siderable part  of  the  year.  Lunularia  is  of  almost  uni- 
versal occurrence  in  greenhouses,  and  while  seldom  if  ever 
found  in  fruit,  almost  always  has  gemmse  in  different 
stages  of  development.  Conocephalus  is  common  and 
abundant  in  moist,  shady  places.  The  floating  species  of 
Riccia  have  a  wide  range,  as  do  also  some  of  the  species 
of  Porella.  These  and  other  genera  will  furnish  a  full 
supply  of  material  for  comparative  study. 

The  student  is  advised  to  proceed  with  his  preliminary 
observations  as  he  did  with  the  mosses,  comparing  a  num- 
ber of  different  kinds,  instead  of  confining  his  attention 
to  a  single  species.  Differences  of  habit  between  these 
and  the  mosses,  the  bilateral  and  dorsi-ventral  frond  of 
the  liverworts,  their  texture  and  anatomical  structure,  and 
peculiarities  of  fructification  should  all  be  noted.  If  the 
mosses  have  already  been  studied  as  directed,  there  will 
be  little  difficulty,  with  suitable  material  and  the  help  of 
the  various  manuals,  in  obtaining  a  corresponding  general 
view  of  the-structure  and  habits  of  the  liverworts. 

Many  interesting  subjects  for  more  extended  investi- 
gation present  themselves ;  among  them  the  following 
are  suggested  as 


MOSSES   AND  LIVERWORTS.  113 

* 

SPECIAL   STUDIES. 

I.  Development  of  the  gemmae.  Lunularia  offers  ex- 
cellent and  abundant  material  for  this,  and  its 
gemmse,  on  account  of  their  simplicity,  are  among 
the  best  objects  with  which  to  begin  studies  of 
developmental  history. 

II.  Comparison  of  the  anatomy  of  Conocephalus  with 
that  of  Marchantia.  The  latter  is  selected  because 
of  its  being  so  fully  described  in  the  books.  For 
the  former,  Lunularia  or  some  other  genus  may 
be  substituted  if  more  convenient. 

III.  Rhizoids  of  liverworts  compared  with  those  of  mosses. 

IV.  Structure  of  the  mature  sporocarp  in  the  different 

families  of  liverworts. 

V.  Comparison  of  the  archegonia  and  antheridia  of 
liverworts  and  mosses. 

VI.  Alternation  of  generations  as  seen  in  mosses  and 
liverworts  compared  with  the  ferns  and  other 
vascular  cryptogams.  This  will  naturally  be  post- 
poned until  after  the  study  of  the  latter  groups.- 
It  will  be  found  that  in  the  ferns  the  oophytic 
generation  is  reduced  to  a  green  prothallium,  and 
in  the  club-mosses  and  their  allies  a  still  further 
reduction  takes  place. 

VII.    Origin  of  the  calyptra  of  mosses. 


114  STUDY   OF   COMMON   PLANTS. 


X.     FERNS.     FILICINE^E. 

MATERIAL   REQUIRED. 

Shield-fern,  Aspidium  cristatum,  Swartz,  gathered  in  summer  when  the 

fructification  is  fully  developed. 
Similar  specimens  of  maidenhair,  Adiantum  pedatum,  L.,  brake,  Pteris 

aquilina,  L.,  spleen  wort,  Asplenium  Filix-fcemina,  Bernh. 
Representatives  of  other  genera  of  ferns  that  are  procurable,  such  as 

Cystopteris,  Woodwardia,  Osmunda,  Dicksonia,  etc. 

SHIELD-FERN.     Aspidium  cristatum,  Swartz. 

General  Characters. 

I.  Record  first  what  you  have  observed  as  to  the  habits 
and  habitat  of  the  plant.     Does  it  grow  in  moist  or  dry 
ground?   in  shady  places  or  in  the  open?      How  do  its 
habits  compare  with  those  of  other  ferns,  as  regards  choice 
of  soil  and  surroundings  ?  l 

II.  Notice  the  parts  of  the  plant. 

1.  The  underground  stem,  from  which  arise 

2.  Large,  compound  leaves,  fronds,  and 

3.  Roots.     Observe  their  origin,  form,  and  structure. 


The  leaf  is  the  most  characteristic  part  of  the  fern,  and  is 
to  be  studied  in  detail.     Notice 

1  Cf.  Underwood,  Our  Native  Ferns  and  their  Allies. 


FERNS.  115 

I.  The  leaf-stalk,  stipe,  with  many  thin,  brown  scales. 
Are  these  persistent  or  deciduous  ? 

II.  The  outline  of  the  frond  and  the  form  of  its  main 
divisions,  pinnae. 

Ill*  How  the  pinnae  are  divided.  Compare  the  descrip- 
tion of  this  species  in  Gray's  Manual,  p.  688. 

IV.  The  venation.  Select  one  of  the  pinnae  in  which 
this  is  well  denned,  and  draw  it  carefully  in  outline,  tak- 
ing pains  to  represent  accurately  the  exact  position  of  the 
veins,  tracing  them  to  the  end  of  their  ultimate  divisions. 

Fructification. 

I.  The  conspicuous  bodies  on  the  under  side  of  the 
pinnae  are  the  sori,  or  fruit-dots.  Observe 

1.  Their  position.     Are  they  situated  on  the   back  or 

alongside  of  the  veinlet? 

2.  The    thin,  scale-like    covering,  indusium,  protecting 

the  spores. 

II.  Taking  specimens  nearly  or  quite  mature,  remove 
the  indusium,  and  with  a  good  lens  look  at  the  spore-cases, 
sporangia.     Mount  in  water  in  the  usual  way,  and  examine 
under  a  low  power  of  the  compound  microscope.     Observe 

1.  The  general  form  and  structure  of  the  sporangium, — 

a  flattened  sac,  the  walls  of  which  are  composed  of 
distinct  cells. 

2.  The  annulus,  a  row  of  thick-walled  cells,  forming  a 

continuation  of  the  stalk.     Does  the  annulus  ex- 
tend completely  around  the  sporangium  ? 

III.  Examine  the  sporangia  under  a  high  power,  observ- 
ing them  in  different  positions.     Compare  different  speci- 
mens and  draw  a  perfect  one. 


116  STUDY  OF  COMMON  PLANTS. 

IV.  Using  material  that  has  been  kept  in  alcohol,  mount 
some  of  the  sporangia  in  water  as  before,  and  examine 
microscopically.     Run  a  drop  of  glycerine  under  the  cover 
glass  and  notice  the  result.     Repeat  the  experiment  until 
you  are  satisfied  as  to  the  way  the  spores  are  discharged 
from  the  sporangium. 

NOTE.  —  This  is  by  no  means  an  easy  problem.  Notice  where  the 
sporangium  ruptures,  the  form  of  the  cells  composing  the  annulus,  and 
the  changes  they  undergo  with  its  change  of  position.  Try  the  use  of 
different  media,  such  as  strong  salt  solution,  etc.  Compare  the  sporangia 
of  different  ferns,  and  see  whether  all  have  the  same  structure  and  behave 
alike. 

V.  Under  the  highest  power,  study  the  form  and  struct- 
ure of  the  spores.     Draw  one  or  more  of  them. 

VI.  Taking  almost  any  sorus  except  the   oldest  ones, 
study   the    development    of    the    sporangium    by    carefully 
comparing  the  structure  at  different  ages.      A  series  of 
drawings  should  be  made  illustrating  as  many  stages  as 
possible.1 

Prothallium. 

If  fern  spores  are  sown  on  soil,  or  on  pieces  of  decayed 
wood,  and  are  kept  in  a  moist  atmosphere,  they  will  germi- 
nate, and  give  rise  to  a  structure  known  as  the  prothallium. 

I.  The  early  stages  of  development  of  the  prothallium 
are  easily  observed  by  examining  the  spores  at  intervals 
during  the  first  few  days  after  they  have  been  sown. 
Microscopic  examination  shows  that  the  spore  swells,  the 
outer  coat,  exospore,  ruptures,  and  the  inner  coat,  endospore, 
protrudes  in  the  form  of  a  papilla,  which  rapidly  elongates 
into  a  delicate,  tube-like  structure,  the  first  root-hair.  The 

1  Cf.  Goebel,  Outlines  of  Classification  and  Special  Morphology,  p.  217 
et  seq. 


FEKNS.  117 

spore  itself  elongates  at  the  same  time  and  becomes  sep- 
tate, the  septa  at  first  arising  at  right  angles  to  its 
direction  of  growth.  By  further  growth,  and  a  series  of 
divisions  in  different  directions,  the  mature  prothallium 
is  finally  produced.  While  the  prothallium  is  in  the 
early,  or  filamentous  stage  of  its  development,  the  form 
and  contents  of  its  cells  and  other  structural  details  are 
easily  observed.  Full  descriptions,  accompanied  by  care- 
ful drawings,  should  be  made.1 

II.  The  mature  prothallium  may  be  raised  successfully 
by  taking  care  of  the  specimens  that  have  been  started 
as  directed  above;  but  since  they  require  weeks,  or  even 
months,  to  attain  their  full  development,  it  is  more  con- 
venient to  obtain  prothallia  from  conservatories  where 
ferns  are  cultivated.  In  the  pots  containing  ferns,  or  on 
the  surface  of  the  moist  earth  near  by,  one  can  frequently 
find  excellent  specimens.  They  are  generally  heart-shaped, 
a  few  millimeters  to  a  centimeter  in  diameter,  of  a  delicate 
green  color,  and  so  much  like  small  liverworts  as  some- 
times to  deceive  experienced  collectors. 

An  uninjured  specimen  that  has  been  carefully  washed,  so 
as  to  remove  the  adherent  particles  of  earth,  shows  under 
the  microscope  a  deep  anterior  depression,  sinus,  and  back 
of  this  a  thickened  portion  of  the  prothallium,  sometimes 
called  the  cushion.  The  latter  is  several  layers  of  cells  in 
thickness,  while  the  parts  nearer  the  margin  are  but  one 
layer  thick.  Rhizoids  in  great  numbers  arise  from  the 
lower  surface.  The  growing  point  is  at  the  base  of  the 
depression.  The  arrangement  of  the  cells  at  this  point 
indicates  their  order  of  development,  which  is  readily 

1  For  a  model  cf.  Campbell,  Development  of  the  Ostrich  Fern. 
Memoirs,  Boston  Soc.  Nat.  Hist.,  Vol.  IV,  No.  II  (1887). 


118  STUDY  OF  COMMON  PLANTS. 

made  out  if  younger  specimens  of  different  ages  are  com- 
pared. 

After  the  points  named  have  been  observed,  drawings  of 
the  mature  prothallium  should  be  made  and  compared  with 
those  of  earlier  stages.  If  the  material  is  suitable  for  the 
purpose,  intermediate  stages  of  development  also  may  be 
studied. 

III.  On  the  lower  side  of  the  mature  prothallium  arche- 
gonia  and  antheridia  are  produced.  These  are  organs  of 
reproduction,  corresponding  in  function  to  the  "essential 
organs  "  of  flowering  plants.  The  archegonia  are  usually 
situated  near  the  sinus.  They  are  flask-shaped  bodies,  the 
lower  portion  of  which  is  sunk  in  the  tissue  of  the 
prothallium,  while  the  neck  projects  above  the  surface. 
The  neck  consists  of  a  wall  made  up  of  four  longitudinal 
rows  of  cells,  surrounding  a  single  row  of  canal-cells  which 
leacT  down  to  the  obsphere.  The  latter  is  the  cell  from 
which,  after  fertilization,  the  embryo,  i.e.  the  young  frond, 
arises. 

The  antheridia  are,  as  a  rule,  more  remote  from  the 
sinus,  and  present  the  appearance  of  small,  hemispherical 
protuberances,  consisting  of  a  wall  one  layer  of  cells  thick, 
which  encloses  the  mother-cells  of  the  anther ozoids.  The 
latter  are  minute,  ciliated,  protoplasmic  bodies,  and  are  the 
active  agents  of  fertilization.  They  are  best  observed  by 
placing  in  water  on  a  slide  prothallia  that  have  been  kept 
rather  dry  for  some  time.  After  the  water  has  been 
absorbed  by  the  antheridium  the  latter  ruptures,  and  the 
antherozoids  in  great  numbers  are  seen  in  active  motion, 
swarming  in  the  field  of  the  microscope  like  so  many 
animalcules.  Under  favorable  circumstances  they  have 
been  seen  to  move  towards  an  archegoniuni  and  'enter 
it,  passing  down  through  the  canal-cells  which  have  now 


FERNS.  119 

become  mucilaginous.  The  union  of  an  antherozoid  with 
the  oosphere  is  necessary  in  order  to  the  subsequent 
development  of  the  latter.1 

Developmental  History  and  Minute  Anatomy.2 

The  oosphere  after  fertilization  becomes  surrounded  by  a 
cell-membrane,  and  is  now  known  as  the  oospore.  It  is 
afterwards  divided  into  two  cells  by  a  septum  nearly 
parallel  with  the  axis  of  the  archegonium.  This  is  fol- 
lowed by  the  formation  of  two  additional  septa  at  right 
angles  with  the  first  and  with  each  other,  the  oospore- being 
thus  divided  into  eight  parts  or  octants.  Further  cell- 
division  takes  place,  and  the  embryo  soon  shows  a  differ- 
entiation into  a  foot,  or  absorptive  organ,  by  which  it  draws 
nutriment  from  the  prothallium,  a  first  root,  leaf,  and  stem. 
The  first  leaf,  root,  and  foot  are  temporary  structures,  all 
of  them,  serving  the  needs  of  the  plant  for  a  comparatively 
short  period.  The  stem,  on  the  other  hand,  is  of  slow 
growth,  but  is  permanent,  and  finally  attains  the  size  and 
structure  that  it  exhibits  in  the  mature  plant;  roots  and 
leaves  arise  from  it,  the  prothallium  finally  disappears,  and 
the  so-called  sporophyte  takes  the  place  of  the  preceding  or 
oophyte  generation. 

1  Only  a  bare  outline  is  given  above.    For  further  details  the  student 
should  consult  $trasburger,  Practical  Botany,  pp.  290-296 ;  Bennett  and 
Murray,  Cryptogamic  Botany,  p.  64  et  seq. ;  Goebel,  Outlines  of  Classifi- 
cation and  Special  Morphology,  p.  198  et  seq.,  and  references  given  by  the 
authors  just  named.    For  some  of  the  most  recent  and  valuable  contri- 
butions see   Campbell,    Development  of  the  Ostrich  Fern,   and  various 
papers  by  the  same  author  in  the  Botanical  Gazette,  Annals  of  Botany, 
and  other  periodicals. 

2  A  practical  study  of  the  developmental  history  of  ferns  requires  more 
time  than  can  possibly  be  given  to  it  in  a  preparatory  course,  and  accord- 
ingly it  is  thought  best  to  omit  altogether  directions  for  laboratory  work, 
merely  giving  a  resume  of  the  cycle  of  development  as  it  has  been  worked 
out  by  different  botanists.     Cf.  Goebel,  I.e.,  p.  204  et  seq. 


120  STUDY    OF    COMMON    PLANTS. 

The  alternation  of  generations  just  referred  to  appears 
very  clearly  in  the  ferns.  The  oophyte,  or  sexual  gener- 
ation, includes  the  stage  beginning  with  the  germination 
of  the  spore  and  closing  with  the  fertilization  of  the 
oosphere.  The  sporophyte,  or  non-sexual  generation,  be- 
gins with  the  formation  of  the  oospore  and  closes  with  the 
mature  spore.  The  prothallium  is,  therefore,  the  charac- 
teristic feature  of  the  oophytic  generation,  and  the  leafy 
plant,  in  this  case  the  "fern,"  of  the  sporophytic  generation.1 

Full  instruction  for  the  study  of  the  minute  anatomy  of 
ferns  is  given  in  a  number  of  accessible  manuals,  and  need 
not  be  repeated  here.  A  quite  full  and  satisfactory  ac- 
count of  Pteris  is  given  by  Sedgwick  and  Wilson  in  their 
General  Biology ;  Adiantum  is  well  treated  by  Arthur, 
Barnes,  and  Coulter  in  the  Plant  Dissection  ;  and  Bower 
and  Vines  give  sufficient  help  for  a  thorough  microscopic 
study  of  Aspidium.  It  appears  to  the  writer  better,  if  the 
time  is  limited,  to  undertake  complete  examination  of 
only  one  part,  preferably  the  stem,  since  the  leaf  repeats 
in  its  general  structure  much  of  what  has  already  been 
seen  in  the  flowering  plants.  In  studying  the  stem,  most 
of  the  time  should  be  given  to  the  nbro-vascular  bundle, 
including  a  comparison  of  its  structure  with  that  of  the 
bundle  of  Indian  corn  and  the  apple  tree.  The  investiga- 
tion may  well  be  extended  to  various  other  plants ;  but  its 
success  will  depend  on  the  preparation  and  judgment  of 
the  teacher,  and  the  previous  training  of  the  student.  On 
the  whole,  a  comprehensive  study  of  the  fibro-vascular 

1  So  much  depends  on  a  correct  conception  of  the  alternation  of  gen- 
erations, that  the  teacher  is  advised  to  review,  illustrate,  and,  in  short,  use 
all  means  to  make  it  clear.  It  stands  as  a  prominent  developmental 
character,  common  to  all  the  groups  of  plants  from  mosses  to  phanero- 
gams. Cf.  Sachs,  History  of  Botany,  pp.  200,  201. 


FERNS.  121 

bundle   hardly  falls  within  the  scope  of   an   elementary 
course. 

RELATIONSHIP. 

A  careful  comparative  study  of  a  number  of  prominent 
genera  of  ferns  should  be  made.  Those  named  above  are 
widely  distributed,  and,  in  general,  easily  procurable.  For 
this  part  of  the  work,  dried  specimens  are  nearly  or  quite 
as  satisfactory  as  fresh  ones.  The  comparison,  while  in- 
cluding a  study  of  external  characters,  should  be  directed 
primarily  to  the  fructification,  which  presents  the  really 
distinctive  features  of  the  different  genera.  It  is  necessary 
in  each  of  the  genera  studied,  to  observe  particularly  the 
form  of  the  sorus  and  indusium,  and  the  way  in  which  the 
latter  is  attached  to  the  leaf.  If  ten  or  a  dozen  different 
kinds  of  ferns  are  studied  in  this  way,  with  accompanying 
drawings  and  descriptions,  the  student  will  have  learned 
from  his  own  observation  the  salient  characters  of  the 
ferns  as  a  group,  the  marks  that  distinguish  the  more 
prominent  genera,  and  the  features  by  which  the  species 
belonging  to  them  are  recognized.1 

The  ferns  include  three  thousand  or  more  species,  vary- 
ing widely  among  themselves  in  habits  and  external  feat- 
ures. With  leaves  of  extraordinary  variety  and  beauty ; 
their  texture  delicate  or  coriaceous,  or  extremely  thin  and 
translucent,  as  in  the  filmy  ferns ;  of  various  habits,  creep- 
ing, climbing,  erect,  or  tree-like  ;  growing  in  every  quarter 
of  the  globe,  and  yet  exhibiting  marked  preferences  of  soil 
and  surroundings ;  a  dominant  group  in  earlier  geological 
time,  and  still  holding  a  manifest  supremacy  among  the 
higher  cryptogams,  —  they  present  themselves  as  one  of  the 
most  varied  and  attractive,  and  at  the  same  time  most  easily 

1  For  further  hints  see  Underwood,  Our  Native  Ferns  and  their  Allies. 


122  STUDY  OF  COMMON  PLANTS. 

studied  groups  of  plants.  They  are  of  special  interest  as 
representatives  of  the  higher  flowerless  plants,  the  vascular 
cryptogams,  since  they  share  with  them  certain  develop- 
mental features  that  are  wanting  or  are  imperfectly  seen 
in  phanerogams.  The  alternation  of  generations  is  far  more 
easily  recognized  here  than  in  flowering  plants,  since  both 
generations  are  characterized  by  structures  of  considerable 
size.  The  oophyte,  or  sexual  generation,  presents  us  with 
the  prothallium,  which  is  a  relatively  conspicuous,  leaf-like 
body,  bearing  archegonia  and  antheridia,  structures  that  do 
not  occur  in  the  same  form  in  phanerogams.1  The  system- 
atic literature  is  extended  and  rather  expensive.  Eaton's 
Ferns  of  North  America  is  the  best  for  this  country,  and 
the  works  of  Hooker  and  Baker  give  the  most  help  on 
foreign  species ;  but  with  Gray's  Manual  or  Underwood's 
little  book,  the  student  will  be  able  to  identify  without 
difficulty  the  ferns  indigenous  to  the  region  where  he  lives, 
and  this  is  suggested  to  him  as  an  interesting  and  instruc- 
tive piece  of  systematic  work. 

1  On  the  homologies  of  these  organs  as  they  exist  in  higher  plants  cf . 
Bennett  and  Murray,  Cryptogamic  Botany,  p.  11  et  seq. ;  Goebel,  Out- 
lines of  Classification  and  Special  Morphology ;  Macraillan,  Metaspermaz 
of  the  Minnesota  Valley,  and  recent  periodical  literature. 


HORSETAILS.  123 


XL     HORSETAILS.    EQUISETINE^E. 

MATERIAL  REQUIRED. 

Common  horsetail,  Equisetum  arvense,  L.  The  fertile  fronds  must  be 
gathered  in  the  spring  when  the  spores  are  mature.  These  are 
preferably  examined  fresh,  but  may  be  preserved  in  alcohol. 
Sterile  fronds  in  the  early  stages  of  development  may  be  gathered 
at  the  same  time,  but  fully  formed  ones  will  have  to  be  obtained 
later  in  the  season,  unless  they  are  pressed  or  put  up  in  alcohol 
the  preceding  year.  Underground  stems,  with  fronds  attached, 
should  be  collected. 

Other  species  of  the  same  genus,  such  as  the  scouring-rush,  Equisetum 
hie'male,  L.,  and  others. 

COMMON   HORSETAIL.     Equisetum  arvense,  L. 
General  Characters. 

I.  Note  first  the  habits  of  the  plant,  the  places  in  which 
it  grows  best,  and  the  time  of  year  when  it  appears  above 
ground. 

II.  Compare  the  two  forms  that  arise  from   the   same 
rootstock,  the  fertile   and   sterile  fronds,  noting   points  of 
likeness  and  difference. 

III.  Examine    the    underground    stem,    observing    its 
peculiarities  of  form,  size,  and  structure  as  compared  with 
the  aerial  stems. 

Fertile  Frond. 

I.    Examine  the  fertile  frond  throughout,  and  describe 
in  detail  its  characteristic  features.     Notice 


124  STUDY   OF   COMMON   PLANTS. 

1.  The  succession  of  nodes  and  inter  nodes.     Are  there 

any  branches  ? 

2.  The  whorls  of  modified  leaves  arising  at  the  nodes. 

How  many  leaves  are  there  at  each  node?  Are 
they  separate  or  united?  Do  they  differ  in  either 
texture  or  color  from  the  stem  ?  If  so,  how  ? 

3.  Surface,   form,   and   structure  of  the  stem.     Cut   a 

transverse  section  of  an  internode  and  examine 
under  a  dissecting  microscope.  Is  it  solid  or 
hollow?  Notice  the  openings,  lacunae,  and  their 
number  and  position.  Are  these  constant  in  differ- 
ent specimens?  Is  there  any  mechanical  advantage 
in  such  a  disposition  of  material  ? 
Make  an  outline  sketch  of  the  section,  using,  if 
necessary,  a  higher  magnifying  power. 

II.  Study   next   the   spike   terminating   the    stem   and 
bearing  the  fructification.     It  will   be    seen  that  it  is  a 
modified  portion  of  the  stem,  showing  a  succession  of  nodes 
and  internodes,  and  exhibiting  more  or  less  perfectly  the 
same  structural  features  as  other  parts  of  the  stem. 

1.  With  a  pair  of  fine  forceps  remove  one  or  more  of 

the  leaves,  here  called  scales,  and  examine  them 
carefully.  Their  study  will  be  facilitated  by 
making  transverse  and  longitudinal  sections  of  the 
spike,  so  as  to  expose  the  scales  more  fully.  Are 
they  stalked  or  sessile  ?  Draw  one  in  outline. 

2.  Examine    under   a   lens    the    spore-cases,   sporangia, 

borne  on  the  under  surface  of  each  scale.  How 
many  are  there  ?  What  is  their  shape  ?  Make  an 
outline  sketch. 

III.  Remove  carefully  one  of  the  sporangia,  mount  in 
water,  and  examine  with  the  compound  microscope.     Be 


HORSETAILS.  125 

sure  to  have  a  well-formed  and  uninjured  specimen. 
Observe  the  peculiar  structure  of  the  cells  that  compose 
the  sporangium  wall.  Ascertain,  if  you  can,  how  the 
sporangium  opens.1  Draw  carefully  a  few  of  the  cells, 
using  the  high  power. 

IV.  Examine  the  spores  under  the  high  power  of  the 
compound  microscope,  mounting  some  of   them  in  water 
and  others  dry.     How  do  the  dry  ones  differ  from  those  in 
water?     Breathe  gently  on  them,  and  see  if  any  changes 
take  place.     Draw  one  or  more  of  the  spores  with  their 
slender,  hygroscopic  appendages,  elaters. 

V.  Sow  some  of  the  spores  in  water  and  others  on  moist 
soil,  and  at  intervals  examine  with  the  microscope.     Germi- 
nation of  the  spores  and  the  early  stages  of  development 
of  the  prothallium  are  easily  observed,  and  should  be  figured 
and  described. 

Sterile  Frond. 

I.  Examine  specimens  of  the  sterile  frond  throughout, 
comparing  them  in  detail  with  the  fertile  ones.     How  do 
they  differ  from  the  latter  in  size,  color,  texture,  formation 
of    branches,   and   structure   on    transverse   section?     Is 
there  a  "division  of  labor"?     If  so,  point  out  what  you 
conceive  to  be  the  most  important  function  of  the  fertile 
frond;  of  the  sterile  frond. 

II.  Study  the  fibro- vascular  bundles,  and  compare  with 
those  of  the  fertile  frond.     Verify  the  details  of  structure 
as  given  by  Goebel,  Outlines  of  Classification  and  Special 
Morphology,  pp.  270-272. 

JCf.  Newcombe,   Spore-dissemination  of  Equisetum,  Bot.  Gaz.,  Vol. 
XIII  (1888),  p.  173. 


126  STUDY   OF   COMMON   PLANTS. 

RELATIONSHIP. 

With  the  species  already  studied  compare  others  of  the 
same  genus,  such  as  Eqwisetum  hiemale,  L.,  E.  limosum,  L., 
etc.  Do  these  species  show  the  same  general  structure  ? 
Do  they  present  the  same  differentiation  into  fertile  and 
sterile  fronds  ? 

Comparison  with  still  other  species  of  the  single  genus  now 
composing  this  family1  shows  that  the  Equisetinese. possess 
very  marked  and  characteristic  features  by  which  they  are 
distinguished  from  all  other  families  of  plants.  At  the 
same  time  their  close  relationship  with  the  ferns  is  evident 
when  their  developmental  history  is  followed  out.  If  the 
spores  of  the  common  horsetail  are  sown  as  directed  above, 
the  development  of  the  prothallium,  including  the  forma- 
tion of  archegonia  and  antheridia,  can  be  observed  in  detail 
in  the  course  of  a  few  weeks,  and  affords  a  most  instructive 
study.2  If  this  study  is  carried  far  enough  to  include  the 
formation  of  the  embryo  and  growth  of  the  young  plant,  it 
is  seen  that  the  cycle  of  development  is  essentially  identical 
with  that  of  the  ferns. 

1  The  horsetails  are  remnants  of  a  family  which  once  flourished  luxuri- 
antly, reaching  its  highest  development  in  the  Carboniferous  period,  when 
there  were  several  genera,  including  a  number  of  tree-like  species. 

2Cf.  Campbell,  Male  Prothallium  of  the  Common  Horsetail,  Arner. 
Nat.,  1883,  p.  10. 


CLUB-MOSSES   AND  THEIR   ALLIES.  127 


XII.     CLUB-MOSSES  AND   THEIR   ALLIES. 
L.YCOPODINEJE. 

MATERIAL   REQUIRED. 

Fresh  specimens  of  Selaginella  from  the  conservatory.  A  number  of 
species  are  common  in  cultivation,  and  any  of  them  may  be  used. 

Club-moss,  Lycopodium  clavatum,  L.,  with  spore-bearing  spikes.  Simi- 
lar specimens  of  other  species  of  the  same  genus,  e.g.  L.  lucidu- 
lum,  Michx.,  L.  complanatum,  L.,  etc. 

Any  other  vascular  cryptogams  that  are  procurable,  as  Marsilia  or 
Isoetes. 

SELAGINELLA.     S.  stolonifera,  denticulata,  etc. 
General  Characters. 

I.  Record  your  observations  of  the  plant  as  a  whole. 
Where  did  it  grow,  and  under  what  conditions  ?    Point  out 
any  peculiarities  of  form,  texture,  or  habit,  by  which  it 
would  readily  be  distinguished  from  ferns. 

II.  Examine  carefully  the  mode  of  branching.     Draw  a 
diagram  to  represent  it.     Is  it  dichotomous  or  monopodial'n 
The  plant  is  said  to  be  bilateral  and  dorsi-ventral ;  show 
how  this  is  true.     How  do  you   distinguish  between  the 
dorsal  and  ventral  aspect  of  the  plant  ?  2 

III.  Describe  the  form  and  arrangement  of  the  leaves. 
Are  they  all  alike  ?     How  many  rows  are  there  ? 

IV.  On   well-developed    specimens,    slender,    root-like 
organs,  rhizophores,  are  to  be  found.     Notice  where  these 

1  Cf.  Bower  and  Vines,  Practical  Botany,  I,  p.  162. 

2  Cf.  Strasburger,  Practical  Botany,  p.  296. 


128  STUDY   OF   COMMON   PLANTS. 

arise,  whether  from  the  lower  (ventral),  or  upper  (dorsal) 
side  of  the  stem.  Where  their  ends  com'e  in  contact  with 
the  soil,  roots  are  produced.  Observe  their  peculiar  mode 
of  branching,  unusual  for  roots. 

Fructification. 

The  fertile  branches  are  not  particularly  conspicuous  and 
may  be  overlooked ;  they  are  readily  recognized,  however, 
by  their  rigid,  erect  habit  and  quadrangular  outline,  in 
contrast  with  the  flattened  and  spreading  sterile  branches. 

I.  Notice    the    form   and   arrangement   of    the   leaves. 
How  do  they  differ  from  those  of  other  parts  of  the  plant  ? 

II.  The  spore-cases,  sporangia,  arise  singly  in  the  axils 
of  the  leaves.     They  are  of  two  kinds,  microsporangia  in 
the  axils  of  the  upper  leaves,  and  macrosporangia,  few  in 
number,  in  the  axils  of  the  lower  leaves  of  the  fertile 
branch.     Examine  different  specimens,  under  a  good  lens, 
until  you  are  satisfied  as  to  the  position  of  the  two  kinds 
of  sporangia  and  their  external  differences. 

III.  With  a  pair  of  fine  forceps  remove  the  upper  part 
of  a  fertile  branch  with  its  microsporangia.     Dissect  care- 
fully on  a  slide,  and  examine  with  the  low  power  of  the 
compound  microscope.     Compare  the  sporangia  as  they  lie 
in  various  positions  and  notice 

1.  The  exact  relation  of  the  sporangium  to  the  stem 

and  leaf,  and  whether  it  is  stalked  or  sessile. 

2.  Its  form  and  mode  of  dehiscence. 

NOTE. —  The  cause  of  the  opening  of  the  sporangium  may  not 
be  obvious,  but  there  is  no  difficulty  in  finding  the  line  of  dehis- 
cence and  observing  the  escape  of  the  spores. 

3.  The  structure  of  the  sporangium  wall. 

4.  The  spores,  set  free  in  great  numbers  when  the  spo- 


CLUB-MOSSES   AND   THEIR   ALLIES.  129 

rangium  opens.  From  their  small  size,  as  com- 
pared with  those  produced  in  the  macrosporangia, 
these  are  called  microspores.  With  the  high  power, 
observe 

a.  The  form  of  the  microspores.     Are  they  strictly 

spherical? 

b.  Their   structure,   particularly  the  spiny  exospore 

and  granular  contents. 

IV.  Remove  a  macrosporangium  from  the  lower  part  of 
a  fertile  branch  and  examine  on  the  slide,  using  first  a 
good  lens,  and  afterwards  the  compound  microscope.  Ob- 
serve 

1.  The  obvious    external    differences   by  which  this  is 

distinguished  from  the  microsporangium. 

2.  The  number  of  spores  contained  in  the  sporangium. 

From  their  relatively  large  size,  these  are  called 
macrospores. 

3.  The  structure  of   the  macrospores.     This  is  readily 

made  out  by  simply  treating  with  potash  solution, 
and  dissecting  away  the  hard  external  coat,  as 
recommended  by  Bower  and  Vines.1  Afyer  removal 
of  the  exospore,  the  smooth,  light-colored  endo- 
spore  is  found,  and  the  contents  of  the  spore,  chiefly 
oil  and  aleurone  grains,  with  the  mass  of  cells 
composing  the  prothallium,  are  plainly  seen.  Sec- 
tioning must  be  resorted  to,  if  these  are  shown 
accurately  in  position;  but  all  of  them  can  be 
recognized  easily  and  satisfactorily  by  following 
the  treatment  suggested. 

NOTE. —  It  is  important  that  these  parts  should  be  clearly  seen 
and  understood.     In  Selaginella  the  prothallium  is  formed  before 

1  Practical  Botany,  I,  p.  173. 


130  STUDY   OF   COMMON  PLANTS. 

the  spore  has  left  the  mother  plant,  and  it  is  still  for  some  time 
enclosed  in  the  macrospore,  which  also  contains  a  large  amount  of 
food  materials.  The  whole  structure  shows  a  likeness  on  the  one 
hand  to  the  spores  of  other  vascular  cryptogams,  and  on  the  other 
to  the  embryo-sac  of  flowering  plants. 

Developmental  History  and  Minute  Anatomy. 

As  in  the  case  of  the  fern,  a  laboratory  study  of  the 
developmental  history  requires  a  special  investigation  ex- 
tending through  some  weeks  or  months.  The  following 
important  features  of  the  cycle  of  development  may  be 
mentioned:  Selaginella,  as  well  as  the  ferns  and  horse- 
tails, is  characterized  by  alternation  of  the.  oophyte,  or 
sexual  generation,  with  the  sporophyte,  or  non-sexual  gen- 
eration. The  latter  differs  widely  from  that  of  the  ferns,  in 
that  instead  of  one  kind  of  spore,  giving  rise  to  prothallia 
which  bear  both  antheridia  and  archegonia,  there  are  two 
kinds,  macrospores,  or  female  (archegonia-bearing)  spores, 
and  microspores,  or  male  (antheridia-bearing)  spores,  are 
produced, —  a  distinct  foreshadowing  of  what  is  seen 
in  flowering  plants,  —  the  microspores  corresponding  to 
pollen-grains,  and  the  macrospores  to  the  embryo-sac  of 
the  ovule.  The  oophyte,  again,  as  compared  with  that 
of  the  ferns,  is  reduced  in  size,  and  all  its  early  stages  of 
development  are  completed  within  the  spore,  reminding  us 
of  similar  facts  in  the  developmental  history  of  phanero- 
gams. The  prothallium  of  the  microspore,  in  particular, 
is  reduced  to  the  low.est  terms,  and  should  be  compared 
\vith  the  two  or  more  vegetative  cells  (rudimentary  pro- 
thallium)  in  the  pollen-grain  of  certain  gymnosperms. 
The  archegonia,  produced  only  on  the  prothallium  of  the 
macrospore,  are  essentially  like  those  of  ferns,  though 
somewhat  simpler,  but  after  fertilization  the  first  septum 
of  the  oospore  is  formed  at  right  angles  to  the  axis 


CLUB-MOSSES   AND   THEIR   ALLIES.  131 

of  the  archegonium,  and  the  upper  of  the  two  cells  thus 
formed  develops  into  a  suspensor,  a  structure  characteris- 
tic of  flowering  plants,  but  occurring  in  few- cryptogams. 

RELATIONSHIP. 

It  is  desirable  that  at  least  the  external  characters  and 
fructification  of  one  or  more  additional  genera  of  vascular 
cryptogams  should  be  studied  in  connection  with  the  pre- 
ceding ones ;  but  specific  directions  are  omitted,  partly 
because  of  uncertainty  as  to  material  likely  to  be  procura- 
ble, and  partly  because  it  is  understood  that  by  this  time 
the  student  should  be  in  a  position  to  make  an  intelligent 
comparative  study  of  at  least  the  general  characters  of 
any  group  to  which  he  has  already  given  special  attention. 
Club-mosses  are  as  likely  to  be  available  as  any  of  the 
Lycopodinese,  since  they  are  pretty  widely  distributed, 
and  besides  are  extensively  used  for  Christmas  decorations. 
As  they  appear  in  market  in  the  middle  of  winter  they  are 
frequently  in  fruit.  Marsilia  and  Isoetes  are  of  great 
interest,  and  when  they  can  be  obtained  may  well  claim 
a  considerable  share  of  the  time  given  to  this  group. 
Aside  from  the  manuals  and  text-books,  the  references 
given  below  will  be  found  serviceable  to  those  who  under- 
take a  further  study  of  the  vascular  cryptogams.1 

1  Campbell,  Development  of  Pilularia  globulifem,  L.,  Annals  of 
Botany,  Vol.  II,  p.  233  ;  Contributions  to  the  Life-History  of  Isoetes, 
Annals  of  Botany,  Vol.  V,  p.  231  ;  On  the  Prothallium  and  Embryo  of 
Osmunda  Claytoniana,  L.,  and  0.  cinnamomea,  L.,  Annals  of  Botany, 
Vol.  VI,  p.  49  ;  On  the  Affinities  of  the  Filicinece,  Botanical  Gazette, 
Vol.  XV  (1890),  p.  1  ;  On  the  Relationships  of  the  Archegoniata,  Botani- 
cal Gazette,  Vol.  XVI  (1891),  p.  323.  Frequent  references  to  other 
important  literature  are  given  by  the  author  in  the  papers  cited. 


132  STUDY   OF  COMMON   PLANTS. 


XIII.    THE   PINE   FAMILY.    CONIFERS. 

MATERIAL  REQUIRED. 

Twigs  of  the  following  species:  White  pine,  Pinus  Strobus,  L. ;  Aus- 
trian pine,  Pinus  A  ustriaca,  Hoess ;  Norway  spruce,  Plcea  exceka, 
Lk. ;  Hemlock,  Tsuga  Canadensis,  Carr. ;  Juniper,  Juniperus  corn- 
munis,  L. ;  Red  cedar,  Juniperus  Virginiana,  L. ;  Arbor  Vitae, 
Thuja  occidentalis,  L. 

Mature  fruits  of  the  preceding,  and  flowers,  both  staminate  and  pis- 
tillate, as  far  as  these  can  be  procured. 

Substitutions,  such  as  Scotch  in  place  of  Austrian  pine,  may  be  made 
as  occasion  requires. 

"WHITE   AND    AUSTRIAN   PINE. 

I.  Compare  branches  of  the  two  species  as  to  surface 
markings  and  other  external  characters. 

II.  Compare  the  foliage  leaves. 

1.  How  many  are  produced  in  a  fascicle?     Examine 

specimens  enough  of  both  species  to  determine  the 
general  rule,  since  exceptions  frequently  occur. 

2.  How  do  those  of  the  two  species  differ  in  length, 

thickness,  rigidity,  and  color  ? 

3.  With  a  sharp  knife  make  a  transverse  section  of  a 

leaf  of  each  kind.     Examine  with  a  lens  and  note 
difference  of  outline. 

III.  Examine  next  the  different  sorts  of  scale-like  leaves. 
Notice 

1.   Differences  of  size  and  texture. 


THE   PINE   FAMILY.  133 

2.  Whether  they  are  deciduous  or  persistent.  Do  the 
two  species  agree  in  this  respect? 

IV.  Study  cones  of  the  two  species,  and  note  the  points 
in  which  they  agree  or  differ. 

V.  Extend  the  comparison,  if  practicable,  to  the  stand- 
ing trees,  observing  their  mode  of  branching  and  other 
characteristic  features. 

VI.  Finally,  passing  in  review  all  the  points  to  which 
attention  has  been  called,  summarize  your  observations  in 
a  brief  written  description,  taking  care  to  bring  out  clearly 
the  distinctive  characteristics  of  each  species. 

NORWAY    SPRUCE.     HEMLOCK. 

Determine  in  what  respects  the  Norway  spruce  differs 
from  the  pines.  Is  the  arrangement  of  the  branches  the  same? 
How  do  the  leaves  compare  in  size,  form,  and  mode  of  inser- 
tion with  those  of  the  pines?  Compare  the  terminal  buds. 
Is  there  anything  common  to  the  cones  of  the  two  species 
of  pines  riot  belonging  to  those  of  the  Norway  spruce? 
Do  the  seeds  of  the  latter  differ  in  any  structural  par- 
ticular from  those  of  the  former  ? 

In  the  same  way  compare  the  hemlock  with  the  different 
species  already  studied,  noting  arrangement  of  branches, 
position,  form,  and  size  of  leaves,  peculiarities  of  terminal 
buds,  structure  of  cones,  and  other  characteristic  features. 

JUNIPER    AND    RED    CEDAR. 

I.  Compare  the  two  species  and  note  all  points  of  dif- 
ference and  resemblance. 

1.  What  is  the  form  of  the  leaves  of  the  juniper? 
Number  of  leaves  in  a  whorl?  How  do  those  of 
the  red  cedar  compare  in  size,  shape,  and  arrange- 


134  STUDY  OF   COMMON   PLANTS. 

ment  with  those  of  the  juniper?  Are  the  leaves 
of  the  red  cedar  all  alike?  Do  they  all  exhibit 
the  same  arrangement? 

2.  If  the  fruits  are  to  be  had,  study  their  structure  and 

points  of  resemblance  and  difference. 

3.  If  living  specimens  are  accessible,  compare  the  habits 

of  the  two  species.     Which  assumes  the  size  and 
habits  of  a  tree  ?     Is  this  difference  constant  ? 
II.   Next   compare  these  with   the  conifers  previously 
studied.     What   characters   are    common   to   the    juniper 
and  red  cedar  that  do   not  belong    to  the  pine,  spruce, 
and  hemlock  ? 

ARBOR  VITJE. 

I.  Observe  the  form  of  the  leaves  and  their  arrange- 
ment on  the  branches.     Are  the  leaves  all   alike  ?     Do 
they  exhibit  any  structural    peculiarity  not  observed  in 
those  of  the  other  conifers  ? 

II.  Compare  the  cones  with  those  of  other  genera.     Is 
the  arrangement  of  the  scales  the   same?     How  does  it 
compare  with  the  leaf  arrangement? 

When  the  pollen  of  the  different  species  begins  to  be 
shed  in  May,  compare  the  structure  of  the  flowers,  both 
staminate  and  pistillate,  of  as  many  different  conifers  as 
can  be  obtained. 

I.  How  do  the  staminate  flowers  of  the  hemlock  differ 
from  those  of  the   Norway  spruce?     From   those   of  the 
pines?     What  peculiarities  are  presented  by  those  of  the 
red  cedar  ? 

II.  Make  a  similar  comparison  of  the  pistillate  flpwers? 

III.  Of   all  the  species  studied  which  are  monoecious? 
Are  any  of  them  dioecious  ? 


THE   PINE   FAMILY.  135 

Write  a  brief  summary  of  the  particulars  in  which  all  the 
species  thus  far  examined  agree.  These,  with  certain 
features  that  you  have  not  yet  observed,  constitute  the 
family  characters  of  the  Coniferce. 

RELATIONSHIP. 

From  the  preceding  study  it  will  be  easy  to  understand 
something  of  the  relationship  of  plants  and  the  way  this  is 
determined  by  botanists. 

1.  Plants  that  are  related  to  each  other  show  a  mutual 

resemblance.     This  may  be  observed  in 

a.  External  features  and  habits,  including  form,  direc- 

tion of  growth,  etc. 

b.  Structure. 

c.  Reproduction. 

</.  Developmental  history. 

e.  To  some  extent,  physiological  peculiarities.  But 
in  this  respect  closely  related  plants  often  show 
great  differences. 

In  our  study  of  the  conifers  we  have  directed  -our  atten- 
tion chiefly  to  external  features. 

2.  Plants  exhibit  degrees   of   relationship,   those  most 

closely  related  being  most  alike,  while  those  re- 
motely related  are  less  alike. 

3.  Plants    that   are    related   as    parents   and    offspring, 

forming  a  succession  of  individuals  not  to  be 
distinguished  from  each  other  by  any  constant 
differences,  constitute  a  species.  The  white  pine 
is  one  species,  the  Austrian  pine  another,  and 
so  on. 

4.  Closely  related  species  constitute  a  genus.     Thus  the 

various   species  of   pines   together  make  up   the 


136  STUDY    OF   COMMON    PLANTS. 

genus  Pinus,  and  ,the  different  species  of  juniper, 
the  genus  Juniperus.  We  have  thus  far  studied 
one  or  more  representatives  of  each  of  the  genera 
Pinus,  Juniperus,  Picea,  Tsuga,  Thuja. 

5.  Closely    related    genera  constitute   a   family.      The 

genera  just  named,  with  a  number  of  others,  make 
up  the  Coniferse,  or  Pine  family. 

6.  Closely   related   families    constitute    higher   groups, 

sometimes  designated  as  orders,  though  the  usage 
is  not  uniform.  Finally,  orders  (of  flowering 
plants)  are  grouped  together  in  the  great  classes 
gymnosperms,  monocotyledons,  and  dicotyledons. 

The  relationships  here  pointed  out  are  those  of  descent. 
It  is  believed  that  just  as  all  individuals  of  a  species  are 
descendants  of  a  common  ancestor,  so  all  the  species  of  a 
genus  and  all  the  genera  of  a  family  have  a  common, 
though  remote  origin. 

We  shall  have  constant  opportunity  in  our  further  study 
of  plants  to  become  acquainted  with  specific,  generic,  and 
family  characters.  Their  recognition  is  frequently  at- 
tended with  some  difficulty,  and  in  all  cases  the  exercise 
of  careful  judgment  is  required.  In  fact  botanical  work 
consists  very  largely  in  accumulating  evidence  by  which 
degrees  of  relationship  are  determined. 


THE  GRASS   FAMILY.  137 


XIV.     THE   GRASS   FAMILY. 

MATERIAL   REQUIRED. 


Entire  plants  of  cultivated  wheat,  soon  after  it  has  headed  out. 

Similar  specimens  bf  the  following  grasses  :  Chess,  Bromus  secalinus,  L.  ; 
Quick-grass,  Ayropyrum  repens,  Beauv.  ;  Orchard-grass,  Dactylis 
ylomerata,  L.  ;  Fowl  meadow-grass,  Glyceria  nervata,  Trin.;  Barn- 
yard-grass, Panicum  Crus-galli,  L.  ;  Indian  rice,  Zizania  aquatica, 
L.  ;  Bur-grass,  Cenchrus  tribuloides,  L.  ;  Beard-grass,  Andropogon 
furcatus,  Muhl.  ;  Timothy,  Plileum  pratense,  L.  ;  June  grass,  Poa 
pratensis,  L. 

Some  of  these  can  be  obtained  in  a  suitable  condition  for  study  early 
in  June  in  the  northern  States,  and  at  a  still  earlier  date  farther 
south  ;  others  are  best  examined  in  late  summer  or  autumn.  Rye 
may  be  used  instead  of  wheat,  and  other  substitutions  may  be 
made  if  necessary. 

WHEAT.     Triticum  vulgare,  Villars. 
General  Characters. 

I.  Taking  a  number  of  entire  and  uninjured  specimens, 
determine  first  the  relation  of  the  stem  and  root  system. 
Is  there  anything  to  show  whether  more  than  one  culm  is 
produced  from  a  grain  of  wheat  ?     "  By  the  process  of  til- 
lering, or  multiplication  of  stems  from  one  root  .  .  .  over 
fifteen  hundred  grains  have  been  obtained  from  a  single 
seed."     The  beginnings  of  this  process  may  be  observed  in 
seedlings  of  wheat  started  in  the  laboratory. 

II.  Examine  the  stem,  culm,  and  note  all  peculiarities  of 

1  The  Graminese  will  be  studied  to  better  advantage  after  some  other 
families  of  monocotyledons,  such,  for  example,  as  the  Liliaceae, 


138  STUDY    OF    COMMON    PLANTS. 

form  and  structure.  Is  any  mechanical  principle  involved 
in  the  disposition  of  material  ?  Observe  the  number  and 
position  of  the  nodes  (parts  of  the  stem  to  which  the  leaves 
are  attached).  Do  they  contribute  in  any  way  to  the 
strength  of  the  structure  ? 

Bend  the  culm  through  several  degrees,  after  stripping 
off  the  leaves.  Where  are  the  weakest  parts  ?  Is  there 
any  special  protection  or  support  for  these  parts  ? 

Taken  as  a  whole,  is  the  stem  satisfactorily  constructed  to 
sustain  the  weight  of  the  head  and  resist  the  stress  of  winds? 

NOTE. —  Microscopic  examination  shows  a  simple  but  effective  arrange- 
ment of  the  mechanical  elements  of  the  culm,  by  which  great  strength  is 
secured  with  a  minimum  of  material.1 

III.  Take  up  next   the   relation  of   leaves  and   stem. 
How  are  the  leaves  attached  ?     Are  their  sheaths  entire  or 
slit?     What  is  the  leaf  arrangement? 

IV.  Note  the  form  and  structure  of  the  leaves,  arid  the 
manner  in  which  they  twist  in  drying.2 

Notice  the  appendage  of  the  leaf  at  the  angle  made  by 
the  blade  and  culm.  What  is  it  morphologically,  and 
what  is  it  called  ?  3 

Inflorescence  and  Flowers. 

I.  Notice  first  the  general  features  of  the  inflorescence. 
It  has  the  form  of  a  thickened  spike,  composed  of  many 
spikelets.    The  latter  are  arranged  alternately  on  each  side  of 
a  "  zigzag,  jointed,  channelled  rachis."   Remove  half  a  dozen 
or  more  of  the  lower  spikelets  to  make  this  more  obvious. 

II.  Study  next  the  structure  of  one  of  the  spikelets. 
Each  spikelet  includes  several  flowers  and  is  subtended  by 

1  Cf.  Haberlandt,  Physiologische  Pflanzenanatomie,  p.  114  et  seq. 

2  Cf.  Beal,  Grasses  of  North  America,  p.  29  et  seq. 

3  Cf.  Gray,  Structural  Botany,  p.  106. 


THE   GRASS    FAMILY.  139 

two  glumes.  Observe  the  form  and  texture  of  the  glumes. 
Are  they  symmetrical  or  one-sided  ?  Is  their  surface 
smooth  or  hairy?  Are  there  any  longitudinal  ribs  or 
"  nerves "'  ? 

III.  Ascertain  how  many  flowers  there  are  in  a  spikelet. 
•Each  of  the    fully  developed  flowers  is  subtended  by  a 
floral  glume  and  a  palet.     The  former,  in  the  bearded  vari- 
eties of  wheat,  bears  at  its  apex  a  long,  barbed  awn. 

IV.  Compare  carefully  the  floral  glume  and  palet,  not- 
ing their  differences  of  form,  position,  and  structure. 

V.  Separate  the  floral  glume  and  palet  so  as  to  expose 
the  parts  of  the  flower  within.     Examine  flowers  of  differ- 
ent ages   until  the   essential   organs   are   found    in    good 
condition.     How  many  stamens  are    there?     How  many 
stigmas?     Look   for   some  minute,  scale-like  bodies,  lodi- 
cules.     How  many  are  there,  and  where  are  they  placed  ? 

VI.  Construct  a  diagram  of  the  flower,  showing  the 
position  of  the  floral  glume,  palet,  lodicules,  stamens,  and 
pistil.1 

VII.  Open  different  flowers  of  the  same  head,  and  con- 
tinue the  examination  until   the  relations  of  anther  and 
stigma  are  ascertained.     Does  it  appear  that  the  flowers  of 
wheat  are  cross-  or  self-fertilized.2 

RELATIONSHIP. 

Obtain  good  specimens  of  any  of  the  genera  named 
above,  and  compare  them  with  wheat  throughout,  noting 
all  points  of  difference  and  agreement.  Chess  is  excellent 

1  Cf.  Eichler,  Bluthendiagramme,  p.  119  et  seq.     Some  interesting  sug- 
gestions are  given  by  Allen,  Flowers  and  their  Pedigrees,  p.  160  et  seq. 

2  Cf.  Seal,  I.e.,  p.  37  et  seq. 


140  STUDY    OF   COMMON    PLANTS. 

to  begin  with,  on  account  of  the  simplicity  and  distinct- 
ness of  its  floral  structures.  Many  of  the  other  genera 
are  likely  to  prove  rather  troublesome  until  the  student 
has  had  some  experience. 

After  careful  comparison  of  as  many  different  kinds  of 
grasses  as  practicable,  summarize  your  observations  in  a 
general  account  of  the  characters  of  the  Graminese. 

This  family  includes  some  four  thousand  species  and  is 
of  great  economical  importance,  since  it  furnishes,  directly 
or  indirectly,  by  far  the  larger  part  of  the  food  of  the  human 
race.  Botanically  it  presents  many  points  of  interest. 
While  there  are  many  species  of  grasses  within  the  tropics, 
they  form  a  characteristic  "sod"  only  in  the  cooler % parts 
of  the  world.  Some  depart  so  widely  from  the  habits  of 
those  we  have  studied  as  to  be  properly  reckoned  among 
climbing  plants.  Although  giving  evidence  of  very  con- 
siderable modification,  the  flowers  are,  with  few  exceptions, 
destitute  of  odor  and  attractive  colors,  and  are  either  self- 
fertilized  or  depend  for  fertilization  on  the  agency  of  the 
wind.  The  seeds  are  disseminated  in  a  variety  of  ways, 
some  passing  undigested  through  the  alimentary  canal  of 
herbivorous  animals,  others,  as  Cenchrus,  bearing  hooked 
or  spiny  appendages,  and  still  others,  as  Stipa,  provided 
with  a  twisting  awn  that  attaches  itself  to  the  coats  of 
animals  or  buries  the  grain  in  the  earth.  In  Tripsacum 
the  joints  of  the  spike  break  apart  and  are  often  floated 
away  by  water,  while  species  of  Panicum  and  Eragrostis 
are  blown  about  by  the  wind  as  "  tumble-weeds."  The 
cultivation  of  the  most  important  grains  is  prehistoric  and 
their  origin  uncertain.1 

1  Cf.  De  Candolle,  Origin  of  Cultivated  Plants,  p.  354  et.  seq. ;  Hackel, 
The  True  Grasses ;  Beal,  Grasses  of  North  America. 


THE   SEDGE   FAMILY.  141 


XV.    THE   SEDGE   FAMILY.    CYPERACE^E. 

The  study  of  this  family  involves  no  little  difficulty,  and  its  various 
genera  present  such  wide  differences  that  it  is  impossible  to  select 
one  that  may  be  taken  strictly  as  a  "  type."  Nevertheless,  it  is 
desirable  that  at  least  the  conspicuous  and  widely  distributed 
genus  Carex  should  be  familiarly  known. 

As  a  convenient  representative,  we  select  one  of  the  most  common 
species. 

CAREX.     C.  hystricina,  Muhl. 
General  Characters. 

Note  the  locality  and  choice  of  surroundings,  the  habit 
of  growth,  whether  in  clumps  or  scattered,  the  height  to 
which  the  plant  grows,  and  general  resemblance,  if  any,  to 
other  plants  already  studied. 

Stem  and  Leaves. 

I.  Notice  the  form  and  structure  of  the  culm.     How 
does  it  differ  from  that  of  wTheat  and  other  grasses  ? 

II.  Note  the  relation  of  stem  and  leaves.     In  how  many 
ranks  are  the  latter  disposed  ?     How  do  their  sheaths  differ 
from  those  of  the  grasses  ?     Is  there  a  ligule  ? 

III.  Describe  the  leaves  as  to  form  and  surface.    Observe 
their  behavior  in  drying. 

Inflorescence  and  Flowers. 

I.  How  many  inflorescences  are  there?  Are  they  sessile 
or  stalked? 


142  STUDY   OF   COMMON   PLANTS. 

II.  Beginning  with  the  lowest  inflorescence,  study  care- 
fully the  individual  flowers.     Note  first  that  each  flower 
is  borne  in  the  axil  of  a  bract  or  scale.     Describe  the  latter 
as  to  form,  color,  and  structure. 

III.  Each  flower  is  further  protected  by  a  sac  called  the 
perigynium.     Examine    this,  observing  critically  its  form 
and  surface,  venation,  and  the  long  beak  terminating  above 
in  two  sharp  teeth. 

IV.  Open  the  perigynium  and  examine  the   pistillate 
flower.     It  consists  of  a  single  pistil,  which  in  some  species 
of  Carex  has  two  stigmas  with  a  lenticular  ovary,  caryopsis, 
while  in  others  the  caryopsis  is  triangular,  and  the  stigmas 
are  three  in  number.     Which  do  you  find  to  be  the  case  in 
this  species  ? 

V.  Taking  younger  specimens,  examine  the  uppermost 
(staminate)    spikes.     How   do    they    differ    in    external 
features   from   the   pistillate   ones  ?     Is  each  flower  sub- 
tended by  a  scale  ?     Does  it  have  a  perigynium  ?     How 
many  stamens  are  there  ? 

VI.  From  the  observed  facts,  what  do  you  infer  as  to 
the  mode  of  fertilization  ? 

RELATIONSHIP. 

A  number  of  other  species  should,  if  possible,  be  com- 
pared with  the  one  just  studied.  Carex  lupulina,  utricu- 
lata,  stricta,  gracillima,  laxiflora,  Pennsylvania,  rosea,  etc., 
are  of  common  occurrence  and  suitable  for  such  a  com- 
parison. The  beginner  will  do  well  to  heed  Professor 
Bailey's  remark  to  the  effect  that  this  is  "  an  exceedingly 
critical  genus,  the  study  of  which  should  be  attempted 
only  with  complete  and  fully  mature  specimens."  After 


THE   SEDGE   FAMILY.  143 

becoming  familiar  with  several  representatives  of  the 
genus  Carex,  some  time  may  be  given  to  a  few  other 
genera  of  Cyperacese,  as,  for  example,  Cyperus,  Eleo- 
charis,  Scirpus,  and  Eriophoruin.  An  intelligent  compari- 
son of  a  limited  number  of  well-developed  and  well-chosen 
forms  will  place  the  student  in  a  position  to  continue 
his  work  satisfactorily ;  but  the  study  of  sedges  demands 
clear  judgment  and  unlimited  patience,  and  will  never 
prove  attractive  to  any  one  who  is  not  possessed  of 
these  qualities.  For  classification,  Gray's  Manual,  sixth 
edition,  will  serve  a  good  purpose.  Professor  L.  H. 
Bailey's  Types  of  the  G-enus  Carex,  Memoirs  of  the  Torrey 
Botanical  Club,  Vol.  I,  No.  I,  is  the  most  important  con- 
tribution that  has  yet  been  made  to  our  knowledge  of 
North  American  species. 


144  STUDY   OF   COMMON   PLANTS, 


XVI.  THE  ARUM  FAMILY.  ARACEJE. 

MATERIAL  REQUIRED. 

Entire  plants  of  Indian  turnip,  Ariscema  triphyllum,  Torr.,  in  flower. 
Similar  specimens  of  skunk-cabbage,  Symplocarpus  fcetidus,  Salisb. 
Flowers  of  cultivated  calla,  Richardia  Africana,  Kunth. 
Other  plants  of  this  order  that  are   procurable,   such  as  sweet-flag, 
Acorus  Calamus,  L.,  and  any  of  the  cultivated  aroids. 

INDIAN   TURNIP.     Ariscema  triphyllum,  Torr. 
General  Characters. 

Examine  entire  specimens  in  a  fresh  condition.     Note 

I.  The  thick,  rounded,  underground  stem,  conn,  more  or 
less  wrinkled  externally. 

II.  Long  fibrous  roots  growing  out  from  its  upper  part. 

III.  Above  ground,  the  smooth,  cylindrical  stem  with 
membranaceous,  sheath-like  leaves  below,  and  one  or  two 
large,  compound,  foliage  leaves  above.     Describe  the  latter 
in  detail. 

IV.  The  peculiar  venation,   differing  from   that   of   a 
majority  of  monocotyledons.     Sketch  one  of  the  leaflets  in 
outline,  and  point  out  the  mechanical  advantages. 

V.  Note  the  acrid  taste  due  to  the  mechanical  effect  of 
the  raphides  (crystals)  on  the  tongue  and  throat. 

Inflorescence  and  Flowers. 

I.  The  inflorescence  is  covered  by  a  peculiarly  shaped, 
arched  spathe.  Compare  this  in  a  number  of  specimens, 
and  note  variations. 


THE   ARUM   FAMILY.  145 

II.  Open  a  spathe  so  as  to  explore  the  parts  within. 
Observe 

1.  The  elongated,   club-shaped,  sterile   portion,  of   the 

spadix. 

2.  The  lower,  fertile  part,  on  which  the  naked  flowers 

are  borne. 

III.  Examine    the   flowers   of    a   number   of    different 
individuals.     It  will  be  seen  that,  as  a  rule,  some  have 
only  pistillate    flowers  and   others    only  staminate   ones. 
Notice 

1.  The  very  simple  structure  of  the  staminate  flowers 

and  the  mode  of  dehiscence  of  their  anthers. 

2.  The  closely  packed   pistillate  flowers,   each  with  a 

sessile,  white  stigma.  Make  sections  and  ascertain 
the  structure  of  the  ovary,  and  the  number  and 
position  of  the  ovules. 

IV.  Ascertain   by  a  further  comparison   of   specimens 
whether  this  species  is  strictly  dioecious. 

V.  If  Ariscema   Dracontium,  Schott.,  can  be  obtained, 
compare    it    throughout    with    the    species   just    studied, 
noting  carefully  all  points  of  likeness  and  difference. 

» 

SKUNK-CABBAGE.     Symplocarpus  fcetidus,  Salisb. 

General  Characters. 

The  skunk-cabbage  is  in  flower  very  early  in  the  season. 
Its  striking  features  at  once  attract  attention.  The  dis- 
agreeable odor,  suggesting  its  common  name,  the  thick, 
shell-like  spathe  enclosing  the  large,  rounded  spadix,  the 
ample  leaves,  and  numerous  long,  fleshy  roots,  arising 
from  the  thickened  rootstock,  mark  this  as  an  exceed- 


146  STUDY  OF  COMMON  PLANTS. 

ingly  well-defined  species.  Record  what  you  have  ob- 
served regarding  the  habitat  and  duration  of  the  plant, 
and  any  other  characters  not  mentioned  above.  Do  its 
habits  indicate  that  it  is  indigenous  ? 

Inflorescence  and  Flowers. 

I.  In  studying  the  plant,  remove  the  spathe,  observing 
meantime  whether  any  special  devices  exist  for  the  attrac- 
tion of  visitors. 

II.  Examine  the  spadix  carefully,  comparing  it  in  plants 
of  different  ages.     The  flowers  are  said  to  be  proterogynous. 
Is  the  statement  confirmed  by  your  observation  ? 

III.  Satisfy  yourself  by  a  further  comparison  of  speci- 
mens whether  self-fertilization  is  possible.1 

IV.  Examine  the  individual  flowers,  making   sections 
for  this  purpose  that  will  show  their  structure  and  rela- 
tion  to   the  axis  of   inflorescence.     Are    all   the  flowers 
perfect?     How  do  the  stamens  of  older  flowers  differ  from 
those  less  developed  ? 

V.  Construct  a  diagram  showing  the  plan  of  the  flower. 

CALL  A.     Richardia  Africana,  Kunth. 

Compare  the  inflorescence  and  flowers  of  the  cultivated 
calla  with  those  of  the  preceding  species.     Note 

I.  The  color  and  form  of  the  spathe. 

II.  The  structure  of  the  flowers.     Are   they  perfect? 
Are  there  any  floral  envelopes  ? 

III.  How  do  those  of  the  upper  part  of  the  spadix  com- 
pare with  those  of  the  lower  portion  ? 

1  Cf.  Trelease,  Am.  Nat.,  September,  1879. 


THE    ARUM    FAMILY.  147 

A  comparative  study  should  be  made  of  such  other 
aroids  as  can  be  procured,  e.g.  sweet-flag,  water-arum,  etc. 
Aside  from  the  peculiarities  of  their  inflorescence,  which 
mark  them  as  a  unique  group,  the  acrid  properties  of 
many  members  of  this  family  constitute  a  marked  feature.1 

1  Miiller,  Fertilization  of  Flowers,  pp.  562-565,  should  be  consulted. 
Some  interesting  facts  and  suggestions  are  given  by  Allen,  Flowers  and 
their  Pedigrees,  pp.  236-266.  Certain  peculiarities  of  fruits  and  seeds 
may  be  looked  for  as  different  genera  are  examined,  such  as 

1.  The  gelatinous  outer  surface  of  the  fruit  of  Peltandra. 

2.  The   seeds,  —  albuminous   in   some  genera  and   exalbuminous  in 
others. 

3.  The  embryo,  —  green  in  a  number  of  genera. 


148  STUDY    OF   COMMON    PLANTS. 


XVII.    THE    LILY   FAMILY.    LILIACE^E. 

MATERIAL    REQUIRED. 

Yellow  adder's-tongue,  Erythronium  Americanum,  Ker.,  in  flower. 
Representatives  of   other  conspicuous  genera  of  this  family,  as  for 

example  :  Convallaria,  Ornithogalum,  Smilacina,  Uvularia,  Lilium, 

etc. 

Taking  any  of  the  plants  named  above,  when  in  full 
bloom,  examine  the  structure  of  the  flower,  studying  it 
whorl  by  whorl,  as  directed  in  the  case  of  Trillium,  Sec- 
tion VI. 

Comparison  of  even  a  few  genera  of  Liliacese  is  sufficient 
to  show  very  wide  differences  of  external  features.  At 
the  same  time  the  regularity  and  fixed  plan  of  the  flower 
afford  constant  and  distinctive  characters  by  which  the 
immediate  recognition  of  the  family  is  assured.  The 
student,  however,  should  compare  the  flowers  of  a  num- 
ber of  different  species  until  their  morphology  is  perfectly 
familiar.  This  is  the  more  important,  inasmuch  as  the 
flower  of  the  Liliacese  serves  as  a  type  with  which  to  com- 
pare the  modified  flowers  of  a  number  of  related  families 
of  monocotyledons. 

The  family  includes  about  sixteen  hundred  species,  in- 
habiting chiefly  the  temperate  and  warmer  regions  of  the 
globe.  Many  of  the  most  pleasing  and  widely  cultivated 
ornamental  plants,  among  them  the  tulip,  lily,  hyacinth, 
and  lily-of-the-valley,  belong  to  this  family.  With  them 
are  also  included  such  medicinal  plants  as  aloe,  sarsapa- 


THE    LILY    FAMILY.  149 

rilla,  etc.,  and,  among  vegetables,  the  onion,  asparagus, 
and  some  others.  The  extraordinary  extent  to  which  the 
vegetative  organs  have  been  modified,  as  illustrated  by 
the  cladophylls  of  asparagus  and  Ruscus,  indicate  a  com- 
paratively remote  origin,  notwithstanding  the  relative  sim- 
plicity of  the  flowers,  some  of  which,  however,  as  the 
Yucca,  exhibit  very  remarkable  relations  to  insects. 

The  student  is  advised  to  extend  his  acquaintance  to  as 
many  genera  as  possible,  and  to  follow  as  far  as  opportunity 
offers,  the  transitional  stages  through  which  it  is  believed 
that  the  more  highly  developed  ones  have  passed.1  See 
Mliller's  admirable  review  of  the  Liliaceee,  Fertilization  of 
Flowers,  pp.  558,  559,  and  the  papers  of  Riley  and  Trelease, 
third  and  fourth  annual  reports  of  the  Missouri  Botanical 
Garden,  1892  and  1893. 

1  A  number  of  interesting  points  for  comparison  will  present  them- 
selves as  the  family  is  studied.'  e.g. 

1.  The  nectaries  which  vary  much  in  different  genera. 

2.  Bulblets  produced  in  the  axils  of  the  leaves  of  Lilium. 

3.  Wide  differences  of  underground  stems.      Contrast  the  creeping 
rootstock  of  Smilacina,  Medeola,  etc.,  with  the  bulb  of  Lilium  and  Scilla. 


150  STUDY  OF  COMMON  PLANTS. 


XVIII.    AMARYLLIS   FAMILY. 
AMARYLLLDACE^E. 

MATERIAL   REQUIRED. 

Flowers  of  the  cultivated  Amaryllis  in  various  stages  of  development. 

Specimens  should  be  selected  that  have  just  opened,  others  more 

advanced,  and  still  others  that  have  been  open  a  longer  time.     In 

addition  to  these  a  single  entire  plant. 
Other   representatives   of    the   family   that   are   procurable,  such  as 

Hypoxis,  Galanthus,  or  Narcissus,  in  flower. 

I.  In  what  particular  does  the  flower  of  the  Amaryllis 
differ  from  that  of  the  lily  ?     From  that  of  the  Iris  ? 

II.  How  does  the  plant  as  a  whole  differ  from  those  of 
the  Iridacese  that  you  have  studied  ? 

III.  Compare  a  number  of  flowers  of  Amaryllis,  in  differ- 
ent stages  of  development.     What  arrangements  do  you 
find  for  cross-fertilization?     To  what  class  of  visitors  are 
many  of  the  plants  of  this  family  adapted  ? 1 

IV.  Having  examined  as  many  plants  of  the  Amarylli- 
dacese  as  are  to  be  had,  enumerate  the  essential  features 
that  they  possess  in  common. 

V.  Finally  point  out  the  characters  in  which  all  three 
families,  Amaryllidacese,  Iridacese,  and  Liliacese,  agree. 

The  close  relationship  of  these  three  families  of  plants  is 
obvious  upon  acquaintance  with  even  a  few  species.     The 

i  Cf .  Miiller,  Fertilization  of  Flowers,  p.  560. 


THE   AMARYLLIS   FAMILY.  151 

/ 

first  "differs  from  the  Liliacese  in  the  inferior  ovary,"  and 
approaches  the  simple  forms  of  the  Iridacese,  which,  how- 
ever, are  distinguished  by  having  three  stamens  instead  of 
six. 

NOTE.  —  Exercises  of  this  kind  should  be  introduced  and  frequently 
repeated,  as  soon  as  the  pupil  is  in  possession  of  a  sufficient  number  of 
observations  to  make  intelligent  comparisons.  By  this  means  the  impor- 
tant fact  will  become  impressed  on  the  mind,  that  groups  of  related 
families  may  be  recognized  by  their  common  characters,  precisely  as  groups 
of  related  genera  are. 


152  STUDY  OF  COMMON  PLANTS. 


XIX.    THE   IRIS   FAMILY. 

MATERIAL   REQUIRED. 

Blue  flag,  Iris  versicolor,  L.,  in  flower. 
Blue-eyed  grass,  Sisyrinchium  angustifolium,  Mill. 
Cultivated  Iris,  Gladiolus,  and  Crocus. 

BLUE   FLAG.     Iris  versicolor,  L. 
Distribution  and  General  Characters. 

I.  Does  the  plant  manifest  a  decided  choice  of  locality? 
Is  there  anything  to  indicate  whether  it  is  an  indigenous 
species  ? 

II.  Notice    the  form   and  arrangement   of   the   leaves. 
They   are  described   as    equitant.     When   studying  other 
species  recall  this  peculiarity,  and  observe  whether  it  is 
characteristic   of   the    family.      How  do    the   bracts   that 
subtend  the  flowers  compare -with  the  stem  leaves? 

III.  Write  a  description  of  the  plant  as  a  whole,  includ- 
ing rootstock,  stem,  and  leaves. 

Flower. 

I.    Study  first  the  morphological  characters. 

1.  Look   over    the   flower,   whorl    by   whorl,   and   see 

whether  you  recognize  each  part. 

2.  Determine  the  plan.      How  many  divisions  of  the 

perianth  are  there?  How  many  stamens  and 
styles?  Does  the  plan  of  the  flower  differ  in  any 
particular  from  that  of  the  lily  (or  Trillium)? 


THE   IRIS   FAMILY.  153 

3.  Study  carefully  the  modifications  exhibited  by  this 
flower,  as  compared  with  the  lily  taken  as  a  type. 
Have  any  parts  been  suppressed  ?  Does  adnation 
occur?  What  are  some  of  the  most  striking  pecu- 
liarities of  form  and  structure  ? 

II.  Examine  each  part  in  detail  with  reference  to  the 
arrangements  for  cross-fertilization. 

1.  Enumerate  the  attractive  features. 

2.  Ascertain  whether  there  is  a  store  of  nectar,  and  if  so 

whether  there  are  any  path-pointers  to  direct  visit- 
ing insects  towards  it. 

3.  Observe    particularly  the   position   of  stamens   and 

stigma. 

a.  Position  of  the  anther  and  its  mode  of  dehiscence. 

b.  Location    of    the    stigmatic    surface.      Examine 

under  a  good  lens. 

"  The  curved  style-branches  have  at  their  tip  a  small 
deltoid  crest  which  turns  slightly  backward.  Under  this 
there  is  a  thin  shelf,  the  upper  surface  of  which  is  covered 
with  minute  hairs,  and  is  moistened  with  a  sticky  secretion. 
This  shelf  is  the  true  stigma."  Verify  this  description  as 
given  by  Dr.  Goodale,  Wild  Flowers  of  America,  p.  34. 

What  do  all  these  peculiarities  of  structure,  color,  and 
arrangement  suggest?  Do  you  regard  self-fertilization  as 
possible  in  this  species?  If  you  infer  that  cross-fertiliza- 
tion takes  place,  show  how  this  is  probably  brought  about.1 

BLUE-EYED    GRASS.     Sisyrinchium  angustifolium,  Mill. 

This  species  is  widely  distributed,  and  continues  to 
flower  for  some  weeks,  so  that  it  can  usually  be  obtained 
for  comparison. 

1  Cf.  Gray,  How  Plants  Behave,  pp.  21, 25  j  Miiller,'  Fertilization  of 
Flowers,  p.  543  et  seq. 


154  STUDY    OF    COMMON    PLANTS. 

I.  With  entire  specimens  make  a  careful  study  of  the 
blue-eyed  grass,  noting  all  the  points  in  which  it  agrees 
with  the  Iris  or  differs  from  it. 

1.  Compare  the  essential  organs  as  to  number,  position, 

and  structure. 

2.  How  does  the  perianth  differ  from  that  of  the  Iris  ? 

3.  Compare  leaves,  stem,  and  roots. 

II.  Record  concisely  the  results  of  your  comparative 
study  of  the  two  genera,  taking  care  to  bring  out  the 
really  essential  features  that  indicate  their  relationship. 

In  like  manner  compare  with  the  two  preceding  species 
any  other  plants  of  this  family  that  can  be  procured, 
as  the  cultivated  Gladiolus  or  Crocus.  Some  of  the  latter 
open  early  in  the  spring,  and  the  study  of  the  Iridacese 
may  begin  with  them  if  more  convenient.  After  studying 
as  many  representatives  of  the  family  as  practicable, 
summarize  your  observations  in  a  brief  synopsis  of  the 
characters  common  to  them  all.  As  a  subject  of  special 
investigation,  a  comparative  study  of  the  arrangements  for 
fertilization  in  the  Iridacese  is  suggested. 


THE   ORCHIS   FAMILY.  155 


XX.    THE   ORCHIS   FAMILY.    ORCHIDACEJE. 

MATERIAL    REQUIRED. 

Yellow  lady's-slipper,  Cypripedium  pubescem,  Willd.,  and  Arethusa, 
Arethusa  bulbosa,  L.,  in  flower.  Other  species  of  Cypripedium  may 
be  substituted  for  the  former,  and  Calopogon  or  Pogonia  for  the  lat- 
ter. If  it  is  impossible  to  obtain  indigenous  species,  various  trop- 
ical orchids  can  be  procured  through  florists  in  the  larger  cities, 
who  will  deliver  them  safely  at  a  distance.  The  expense  is  of 
small  moment  compared  with  what  is  gained  by  having  a  familiar 
acquaintance  with  at  least  two  or  three  representatives  of  a  family 
of  plants  in  which  mechanical  contrivances  for  securing  cross- 
fertilization  have  been  carried  to  the  highest  degree  of  perfection. 

YELLOW   LADY:S-SLIPPER.     Cypripedium  pubescens,  Willd. 
Flower. 

Our  study  will  be  restricted  to  the  flower,  which,  though 
greatly  modified,  has  departed  from  the  type  less  than  those 
of  other  genera,  and  remains  "  as  a  record  of  a  former  and 
more  simple  state  "  of  the  great  family  to  which  it  belongs.1 

I.    Notice  first  the  most  conspicuous  external  features. 

1.  The   nodding  flower,  generally   single,  terminating 

the  leafy  stem. 

2.  The  floral  envelopes. 

a.  Three  sepals,  of  which  the  upper  one  is  the 
largest,  the  two  lower  united  into  one,  but 
showing  at  the  apex  a  trace  of  their  original 
separation. 

1  Darwin,  Fertilization  of  Orchids,  p.  226. 


156  STUDY   OF   COMMON   PLANTS. 

b.  The  petals,  of  which  the  two  lateral  ones  resemble 
the  sepals,  but  are  narrower  and  more  or  less 
twisted,  while  the  lower1  is  developed  into  a 
large  sac,  the  lip  or  labellum. 

3.  The  essential  organs.  These  have  been  greatly 
modified,  and  are  united  above  into  an  organ 
called  the  column.  Note 

a.  The  three  stamens,  the  single  sterile  one  forming 

a  broadly  triangular  body,  the  apex  of  which 
projects  slightly  into  the  opening  of  the  label- 
lum, and  the  two  lateral  fertile  ones,  each 
with  a  large  anther  on  the  under  side. 

b.  The    fleshy    stigma,   arching   under    the    sterile 

stamen,  the  stigmatic  surface  covered  with 
minute  papillae.  This  is  seen  to  better  advan- 
tage after  the  removal  of  »the  floral  envelopes. 

II.  Having  learned  the  parts  of  the  flower,  endeavor 
next  to  understand  their  homologies.  Such  a  study  is 
extremely  interesting,  showing  as  it  does  "  how  curiously 
a  flower  may  be  moulded  out  of  many  separate  organs,  — 
how  perfect  the  cohesion  of  primordially  distinct  parts 
may  become,  —  how  organs  may  be  used  for  purposes 
widely  different  from  their  proper  uses,  —  how  other 
organs  may  be  entirely  suppressed,  or  leave  mere  useless 
emblems  of  their  former  existence,  —  and  finally  .  .  . 
how  enormous  has  been  the  amount  of  change  which  these 
flowers  have  undergone  from  their  parental  or  typical 
form."2 

1  "The  lip  (in  the  Orchidacese)  is  really  the  upper  petal,  i.e.  the  one 
next  to  the  axis,  but  by  a  twist  of  the  ovary  of  half  a  turn  it  is  more  com- 
monly directed  forward,  and  brought  next  to  the  bract." 

2  Darwin,  I.e.,  p.  234. 


THE   OKCHIS   FAMILY.  157 

1.  Compare  the  flower  throughout  with  that  of  the  lily 

(or  Trillium)  previously  studied,  endeavoring  to 
ascertain  the  character  and  extent  of  its  modifi- 
cations. 

a.  How  does  the   ovary  compare  with  that  of  the 

lily  as   regards   adnation  of  the  floral   envel- 
opes? 

b.  In  what  parts  of   the  flower  has  coalescence  oc- 

curred ? 

c.  Has  suppression  of  any  parts  taken  place  ? 

d.  Point    out    the    most   striking    modifications    of 
form.1 

2.  Construct  a  diagram  and  compare  with  that  of  the 


NOTE.  —  The  student  cannot  hope  to  understand  all  of  this  at 
once.  The  distance  between  the  lily  and  the  lady's-slipper  is  too 
great  to  be  bridged  by  a  single  effort  of  the  imagination.  Let  him 
do  his  best  with  the  flower  itself,  then  read  the  references,  then  lay 
the  whole  matter  aside,  and  return  to  it  again  after  other  representa- 
tives of  tthe  family  have  been  studied. 

III.  The  striking  modifications  of  the  flower  of  Cypri- 
pedium  are  correlated  with  the  visits  of  insects  on  which 
it  is  dependent  for  fertilization. 

1.  There  are  certain  peculiarities  likely  to  prove  attrac- 

tive to  insect  visitors.     Enumerate  these. 

2.  Assuming  that  an  insect,  a  bee  for  example,  is  about 

to  pass  into  the  interior  of  the  labellum,  where 
would  it  be  likely  to  enter?  Would  it  probably 
pass  out  by  the  same  opening  ? 

3.  Examine  carefully  the  structural  peculiarities  of  the 

lip.     Find  where  the  tissue  is  thinnest,  and  accord- 

1  Cf.  Gray,  Structural  Botany,  p.  179  et  seq. 

2  Cf.  Goodale,  Wild  Flowers  of  America,  p.  86  ;  Darwin,  Fertilization 
of  Orchids,  pp.  234-246. 


158  STUDY    OF    COMMON   PLANTS. 

ingly  where  the  most  light  is  admitted.  If  the 
insect  crawling  on  the  floor  of  the  labellum  moves 
towards  the  part  that  is  best  lighted,  which  direc- 
tion will  it  take  ?  Are  there  any  path-pointers  ? 

4.  Examine  more  closely  the  pollen  masses.      Notice 

particularly  their  adhesive  inner  surface.  Observe 
the  form  and  structure  of  the  stigma,  and  see 
how  the  pollen  is  retained  when  applied  to  its 
surface. 

5.  Endeavor  to  interpret  these  peculiar  arrangements. 

If  practicable,  observe  the  action  of  visiting 
insects.1 

ARETHUSA.     Arethusa  bulbosa,  L. 

Study  the  flower  as  directed  in  the  case  of  Cypripedmm, 
with  reference  to 

I.  External  features,  such  as  form  and  position  of  parts, 
color,  odor,  etc. 

II.  Morphological  characters. 

Examine  each  whorl  critically.  Determine  the  plan  of 
the  flower  and  no.te  modifications.  In  what  important 
particular  does  the  andrcecium  differ  from  that  of  Cypripe- 
dium? 

Construct  a  diagram,  and  compare  with  that  of  the 
flower  of  Cypripedium.2 

III.  Physiological  adaptations. 

While  plainly  dependent  on  insects  for  fertilization,  the 
flower  of  Arethusa  presents  a  very  different  mechanism 
from  that  of  Cypripedium.  Examine  carefully  the  rela- 

1  Cf.  Miiller,  Fertilization  of  Flowers,  pp.  539-542  ;  Gray,  Am.  Jour. 
Sci.,  XXXIV  (1862),  pp.  420-429 ;  Darwin,  I.e.,  p.  230. 
*Cf.  Goodalc,  I.e. 


THE   ORCHIS   FAMILY.  159 

tive  position  of  anther  and  stigma,  and  endeavor  to  make 
out  for  yourself  how  this  arrangement  prevents  the  appli- 
cation of  its  own  pollen  to  the  stigma  of  a  given  flower, 
and  at  the  same  time  favors  cross-fertilization.1 

RELATIONSHIP. 

This  large  family  of  plants  includes  about  three  thousand 
species,  widely  distributed  in  both  hemispheres,  and  show- 
ing the  highest  specialization  of  the  flower  yet  attained  in 
the  vegetable  kingdom.  Many  of  the  most  conspicuous  and 
curious  kinds  are  tropical  epiphytes,  and  are  frequently 
cultivated  in  conservatories.  As  Miiller  points  out,  the 
family  is  remarkable  for  the  great  differences  of  habit 
exhibited  by  the  different  species,  the  extraordinary  modi- 
fications of  its  flowers,  and  the  great  number  of  seeds 
produced  in  a  single  fruit.  The  differences  of  habit,  some 
being  epiphytic,  others  saprophytic,  and  so  on,  indicate 
great  capacity  of  the  vegetative  organs  for  variation,  and 
the  modifications  of  the  flowers  are  manifestly  correlated 
with  the  visits  of  insects.  Cross-fertilization  is  the  rule, 
but  here  again  "  orchids  show  the  greatest  possible  differ- 
ences, all  of  which,  however,  are  linked  together  by  inter- 
mediate conditions.  We  find  in  this  order,  cleistogamic 
flowers  and  o'pen  flowers  ;  flowers  regularly  or  occasionally 
self-fertilized ;  others  never  self-fertilized,  though  quite 
fertile  to  their  own  pollen  if  it  be  applied  artificially ; 
flowers  absolutely  sterile  to  their  own  pollen,  though  fer- 
tile not  only  to  the  pollen  of  their  own  species  but  even  to 
that  of  other  species  of  their  own  genus ;  finally,  species 
in  which  pollinia  and  stigma  of  the  same  individual  act 
as  fatal  poisons  to  one  another."  2 

1  Cf.  Gray,  How  Plants  Behave. 
2 Miiller,  I.e.,  pp.527,  528. 


160  STUDY   OF   COMMON   PLANTS. 

The  homologies  of  the  flowers  of  orchids  have  been 
discussed  at  length  by  Darwin  and  others.  The  following 
may  be  given  as  a  brief  resume  of  the  most  essential  facts : 

Comparing  the  flower  of  an  orchid  with  a  simpler  one, 
such  as  a  lily,  the  several  whorls  are  seen  to  have  under- 
gone varying  degrees  of  modification.  The  three  sepals 
are  readily  identified,  although  they  are  usually  petal-like 
in  structure,  and  two,  or  sometimes  all  three,  may  have 
undergone  coalescence.  Of  the  three  petals,  the  two 
lateral  ones  are  alike,  while  the  third,  called  the  lip,  is 
enlarged  and  differs  widely  in  form  from  the  other  two. 
The  essential  organs  are  consolidated  into  a  single  body, 
the  column.  In  the  genus  Cypripedium  one  stamen  has 
become  abortive,  while  the  two  remaining  ones  produce 
pollen  ;  in  the  other  genera  of  the  family  only  one  stamen, 
as  a  rule,  is  perfect.  The  ovary  shows  its  origin  in  three 
carpels ;  but  it  is  one-celled,  and  the  three  placentae  are 
parietal. 

Theoretically  it  is  held  that  originally  the  stamens  were 
in  two  whorls  of  three  each,  and  that  in  Cypripedium  the 
staminode  (abortive  stamen)  belongs  to  the  outer  whorl 
and  the  two  fertile  ones  to  the  inner,  while  in  other 
genera,  in  the  great  majority  of  cases,  this  relation  is 
reversed.  For  a  brief  but  satisfactory  statement  of  this, 
with  good  diagrams,  see  Luerssen,  Botanik,  p.  469. 


THE   WILLOW   FAMILY.  161 


XXI.    THE    WILLOW    FAMILY.     SALICACEJE. 

MATERIAL   REQUIRED. 

Branches  of  the  earliest  flowering  willow,  Salix  discolor,  Muhl.,  gath- 
ered in  the  early  spring  before  the  leaves  appear.  Specimens 
with  both  staminate  and  pistillate  flowers  are  wanted.  (Salix 
cordata,  or  other  species  may  be  substituted.)  Similar  branches 
of  different  kinds  of  poplar,  Populus  tremuloides,  Michx.,  and 
other  species. 

WILLOWS. 
General  Characters. 

Beginning  with  the  willows,  observe  the  various  exter- 
nal characters,  such  as 

1.  Form  and  structure  of  buds. 

2.  Color  of  the  bark.     Is  it  smooth  or  rough  ? 

3.  Texture  of  the  twigs.     Are  they  lithe  or  brittle  ? 

NOTE.  —  Such  characters  are  frequently  of  much  more  impor- 
tance than  they  appear  to  be  at  first  sight.  The  twigs  of  some 
species  of  willows  are  extremely  brittle  at  the  base,  and  being 
easily  detached  serve  as  a  means  of  propagation  ;  while  their  color 
and  surface  are  sometimes  so  characteristic  as  to  become  an  impor- 
tant factor  in  classification. 

Flowers. 

I.    Examine  first  the  staminate  catkins. 

1.  Ascertain    what    constitutes    the    individual  flower. 

(Each  flower  is  subtended  by  a  small  hairy  scale.) 

Under  a  lens  determine 

a.  The  shape  of  the  scale. 

b.  Whether  the  margin  is  cut  or  entire. 


162  STUDY  OF  COMMON  PLANTS. 

c.  Where  the  numerous  silky  hairs  are  attached. 
2.  Study  the  flower  itself. 

a.  How  many  stamens  are  there  ? 

b.  Is  a  nectary  (organ  that  secretes  nectar)  present? 

II.  Examine  next  the  pistillate  catkins. 

1.  In  what  respects  do  they  differ  from  the  staminate 

ones  ?     Are  the  scales  alike  in  both  ? 

2.  Note  the  peculiarities  of  the  pistil. 

a.  Its  form. 

b.  Stalked  or  sessile  ? 

c.  Number  and  form  of  stigmas. 

d.  How  many  carpels  compose  the  ovary  ? 

e.  Is  there  a  nectary  ? 

III.  Are  the  flowers  visited  by  insects?    Enumerate  the 
attractions  adapted  to  secure  insect  visits.1 

Fruits. 

When  the  fruits  are  ripe,  observe  their  structure  and 
mode  of  dehiscence,  the  attachment  of  the  seeds  and  their 
peculiarities,  particularly  their  means  of  dissemination. 

Comparison  with  Other  Species. 

Some  days  later,  as  soon  as  they  are  in  proper  condition 
for  examination,  study  the  catkins  of  other  kinds  of  willows 
(Salix  cordata,  Muhl.,  S.  lucida,  Muhl.,  or  other  available 
species),  and  note  all  the  characters  in  which  they  agree 
with  the  species  already  studied. 

POPLARS. 

In  the  same  manner  make  a  careful  study  of  one  or 
more  common  species  of  poplar  and  compare  them  with 
the  willows. 

1  Cf    Muller,  Fertilization  of  Flowers,  p.  524. 


THE   WILLOW   FAMILY.  163 

I.  Note  first  their  external  characters  and  habits,  and 
notice  in  what  respects  they  differ  from  those  of  the  wil- 
lows. Compare 

1.  Bark. 

2.  Buds,  particularly  the  surface  of  the  bud-scales. 

3.  Leaves. 

4.  Branches,  as  to  size,  texture,  and  surface  marking. 

II.  Carry  out,  step  by  step,  a  thorough  comparison  of 
the  inflorescence  and  flowers. 

1.  How  do  the  scales  of  the  poplar  catkin  differ  from 

those  of  the  willows  ? 

2.  Do  the  flowers  of  the  poplar  have  any  structure  that 

is  wanting  to  those  of  the  willows  ? 

3.  Compare  the  number  of  stamens  in  the  two  genera. 

4.  Are  their  fruits  and  seeds  essentially  alike  ? 

III.  Finally,  after   several   species   of  each  have  been 
studied,  record  all  the  characters  in  which  willows  and 
poplars  agree.     The  characters  exhibited  by  all  of  them  in 
common  are  those  of  the  willow  family  (Salicacese). 

SPECIAL   STUDIES. 

I.    Determination    of    species   of    poplar,    by    means   of 

winter  buds. 

II.    Recognition  of   different  species  of  willow  by  size, 
habit,  and  other  external  features. 

NOTE. — The  identification  of  willows  and  poplars  is  attended  with 
some  difficulty,  requiring  long  practice  and  the  exercise  of  critical  judg- 
ment ;  but  it  is  desirable  that  even  beginners  should  observe  how  readily 
the  large-toothed  aspen,  Populus  grandidentata,  may  be  distinguished 
from  Populus  tremuloides  by  its  bud-scales,  how  Salix  lucida  is  at 
once  recognized  by  its  leaves,  and  how  Salix  alba  and  Salix  nigra 
are  distinguishable  from  other  species  by  their  size  and  from  each  other 
by  their  habit,  even  at  a  distance.  Simple  exercises  of  this  sort  may  be 
introduced  occasionally  with  great  advantage. 


164  STUDY   OF   COMMON    PLANTS. 


XXII.    THE   CROWFOOT   FAMILY, 
RANUNCULACEJE. 

MATERIAL   REQUIRED. 

Specimens  of  the  early  crowfoot,  Ranunculus  fascicularis,  Muhl.,  some 

in  flower,  others  in  fruit. 
Similar  specimens,  as  they  can  be  obtained,  of  Anemone  nemorosa,  L., 

and  Caltha  palustris,  L. 
Representatives  of  other  genera,  such  as  Hepatica,  Clematis,  Aquilegia, 

Actsea,  Hydrastis,  etc. 

EARLY    CROWFOOT.     Rununculus  fascicularis,  Muhl. 
Distribution. 

Record  what  you  have  observed  as  to  the  habitat  of  this 
species.  For  the  use  of  the  term  habitat  cf.  Gray,  Struct- 
ural Botany,  p.  366.  Do  you  regard  it  as  indigenous  or 
introduced  ? 

NOTE.  —  This  is  often  a  difficult  question  to  settle.  We  have  to  de- 
pend partly  on  recorded  observations  and  partly  on  what  we  now  see  of 
the  habits  of  the  plant,  the  places  where  it  grows,  the  direction  in  which 
it  spreads,  and  so  on.  Trustworthy  evidence  is  attained  when  competent 
botanists  actually  observe  for  a  period  of  years  and  record  the  stations 
occupied  by  the  species  in  question. 

Observations  of  this  kind  are  of  much  interest,  and  if  properly  con- 
ducted may  be  made  of  great  scientific  value.  Constant  changes  in  the 
vegetation  of  a  given  locality  are  taking  place,  due  either  to  the  introduc- 
tion of  foreign  species  or  to  the  disappearance  of  indigenous  plants,  as 
the  result  of  changed  climatic  and  other  conditions.  Some  introduced 
plants  have  so  taken  possession  of  territory  invaded  by  them  as  to  become 
formidable  rivals  of  the  native  species,  and  even  to  crowd  them  out.  The 
Canada  thistle,  prickly  lettuce,  butter-and-eggs,  hound's  tongue,  and 


THE   CROWFOOT   FAMILY.  165 

many  others  are  among  the  undesirable  accessions  to  our  native  flora, 
some  of  them  extending  over  wide  areas  in  the  course  of  a  few  years. 

In  collecting  data  regarding  the  distribution  of  a  species,  you  should 
first  of  all  record  where  you  have  seen  the  plant  growing.  To  this  add 
any  observations  you  may  have  made  as  to  its  choice  of  locality,  be- 
havior from  year  to  year,  increase  in  number,  liability  to  extermination, 
etc.  To  be  accepted  as  trustworthy,  notes  of  this  kind  must  be  accom- 
panied by  specimens. 

With  perfect  specimens  at  hand  examine  the  parts  of 
the  plant  in  order. 

Koots. 

Describe  their  shape.  What  direction  do  they  take? 
How  do  those  of  last  year  differ  frotai  those  of  the  present 
year?  Are  there  any  fine,  fibrous  roots?  if  so,  where  do 
they  arise  ? 

NOTE. — A  comparison  of  different  specimens  shows  an  interesting 
division  of  labor. 

The  smaller  fibrous  roots  absorb  from  the  soil  water  and  crude  mate- 
rials that  are  passed  on  to  the  leaves.  In  the  latter,  starch  and  other 
reserve  substances  are  produced,  and  are  then  carried  down  to  the  spindle- 
shaped  roots  where  they  are  stored  until  the  next  year.  At  the  time  of 
flowering  the  roots  of  last  year  have  already  become  exhausted,  and  look 
old  and  wrinkled,  while  the  new  ones  that  are  to  take  their  place  have 
not  nearly  attained  their  full  size.  There  are,  then,  three  different  sets 
of  roots  performing  as  many  different  functions.  One  set  is  absorbing, 
another  is  feeding  the  rapidly  growing  plant,  and  the  third  set  is  develop- 
ing into  a  storehouse  in  which  will  be  laid  up  during  the  summer  a  supply 
of  food  for  future  use. 

Leaves. 

Most  of  the  leaves  arise  from  a  very  short  stem,  and 
appear  as  if  they  grew  directly  from  the  roots ;  accord- 
ingly they  are  described  as  "  radical."  One  or  more  leaves 
are  borne  on  the  flowering  stems  and  are  spoken  of  as 
"cauline," 


166  STUDY   OF   COMMON   PLANTS. 

I.  Describe  first  the  radical  leaves.     Compare  specimens 
and  see  whether  the  same  description  will  answer  for  all 
of  them. 

II.  Examine  the  cauline  leaves  of  a  number  of  different 
individuals  and  note  the  various  forms. 

III.  Are  there  any  means  of  protection  ? 

NOTE.  — Do  not  answer  the  question  hastily.  Hairs  on  delicate  plants 
sometimes  protect  their  tissues  against  cold,  sometimes  against  small, 
soft-bodied  animals  that  might  devour  them  or  climb  up  to  the  flowers 
and  steal  the  nectar,  and  again,  the  presence  of  acrid  juice  may  render 
them  distasteful  to  grazing  animals.  See,  if  you  can,  whether  this  plant 
is  protected  in  any  or  all  of  these  ways. 

Flower. 

Study  first  the  plan  of  the  flower.  Are  all  the  parts 
present?  Is  it  a  " regular "  flower ?  Has  any  consolida- 
tion of  parts  taken  place,  or  are  they  all  free  and  distinct  ? 
Describe  by  a  single  word  the  insertion  of  the  floral  en- 
velopes. 

Next,  examine  and  describe  in  detail  the  successive 
whorls. 

I.  Calyx.     How  many  sepals  are  there?     Is  this  num- 
ber constant?      Describe  their  shape,  color,  and  surface. 
How  does  their  position  on  the  flower  bud  correspond  with 
that  taken  when  the  flowers  are  fully  expanded  ?     From 
its  earlier  condition  do  you  infer  anything  as  to  the  func- 
tion of  the  calyx  ? 

II.  Corolla.      Does   the    number   of    petals   correspond 
with  the  number  of  sepals  ?      Remove  two  or  three  and 
examine  them  under  a  lens.     Draw  one  in  outline,  taking 
care  to  represent  the  little  scale  near  the  point  of  insertion. 

Examine  the  scale  carefully.  Lift  up  the  free  edge 
with  the  point  of  a  needle.  Frequently  a  small  drop  of 


THE  CROWFOOT   FAMILY.  167 

nectar  can  be  found  at  its  base.  The  whole  arrangement 
constitutes  a  simple  and  efficient  device  for  protecting  the 
nectar,  and,  at  the  same  time,  leaving  it  accessible  to  visit- 
ing insects. 

III.  Stamens.     How   many?     Are   they  all  alike?     In 
what  order  do  they  ripen?     Study  under  a  lens  the  mode 
of  dehiscence  of  the  anthers.     It  will  usually  be  found 
that  such  facts,  apparently  trivial,  are  really  important. 
In  the  present  case,  after  the  oldest  stamens   begin   to 
shed   their   pollen,    some    little    time    elapses   before   the 
youngest   ones   are   mature,   thus    ensuring   a   supply   of 
pollen  for  visiting  insects  several  days  in  succession,  and 
insects  climbing  over  the  flowers  can  hardly  fail  to  carry 
pollen  from  one  to  another. 

IV.  Pistils.     Study  these  in   flowers  of  different  ages. 
It  will  be  an  advantage  to  make  longitudinal  sections  of 
the  flower.     Notice 

1.  The  elongated  axis,  receptacle,  on  which  the  pistils 

are  inserted. 

2.  The  shape  of  the  pistils.     Draw  an  enlarged  outline 

of  one. 

8.  In  those  that  have  been  properly  sectioned  the  single 
ovule.  Examine  the  latter  in  still  older  specimens 
and  satisfy  yourself  regarding  its  form,  point  of 
attachment,  and  direction  taken  in  the  ovary. 
Compare  mature  fruits  and  seeds  if  they  are  to 
be  had. 
Read  Miiller,  Fertilization  of  Flowers,  p.  74  et  seq. 

RELATIONSHIP. 

We  have  next  to  study  some  of  the  immediate  relatives 
of  the  early  crowfoot.     This  may  be  done  at  the  same 


168  STUDY   OF   COMMON   PLANTS. 

time,  if  specimens  are  procurable,  otherwise  comparisons 
should  be  deferred  until  a  full  supply  of  material  is  at 
hand. 

I.  We  take  first  the   wood    anemone,  Anemone  nemo- 
rosa,  L. 

The  anemone  rises  from  a  creeping  rhizome  that  gives 
off  fine,  fibrous  roots.  The  simple  stem  bears  a  three- 
leaved  involucre  and  a  single  conspicuous  flower.  Each 
leaf  of  the  involucre  is  petiolate,  without  stipules,  and 
divided  into  three  leaflets  that  are  variously  cut  and 
toothed,  the  lateral  ones  often  divided  nearly  or  quite  to 
the  base.  Similar  radical  leaves  arise  from  the  rhizome. 
The  flower  has  a  calyx  consisting  of  five  or  six  (frequently 
more)  white  sepals,  that  are  often  tinged  with  pink,  many 
distinct  stamens,  and  a  less  number  of  carpels  (15-20). 

See  if  your  specimens  agree  throughout  with  the  de- 
scription just  given.  Name  all  the  points  in  which  the 
anemone  and  early  crowfoot  agree  and  those  in  which 
they  differ.  Incidentally  observe  the  arrangements  for 
securing  fertilization.1 

II.  Continuing  our  comparative   study,   we  next  take 
the  marsh  marigold,  Caltha  palustris,  L.,  and  in  the  same 
way  compare  it  throughout  with  the  anemone  and  early 
crowfoot,  noting  as  before  all  points    of   difference   and 
resemblance.      Widely  as  the   vegetative  parts   differ,  it 
is  obvious  that  the  flowers  of  all  three  species  are  almost 
identical  in  their  essential  structural  features. 

The  marsh  marigold  presents  several  attractive  features, 
and  cross-fertilization  is  effected  through  the  agency  of 
insects,  but  self-fertilization  may  also  take  place.  Cf. 
Miiller,  pp.  79,  80. 

i  Cf.  Miiller,  Fertilization  of  Flowers,  pp.  72,  73, 


THE   CROWFOOT   FAMILY.  169 

III.  If  practicable,  the  comparison  should  be  extended 
to  a  number  of  other  species  belonging  to  different  genera, 
as,  for  example,  Hepatica  triloba,  Chaix,  Anemonella  thalic- 
troides,  Spach,  Clematis  Virginiana,  L.,  Aquilegia  Cana- 
densis,  L.,  Actcea  alba,  Bigel,  Hydrastis  Canadensis,  L., 
and  any  other  plants  of  this  family,  wild  or  cultivated, 
that  may  be  available. 

CHARACTERS   OF   THE   RANUNCULACEJB. 

After  such  a  comparative  study,  embracing  as  many 
species  as  possible,  we  may  sum  up  the  characters  that 
distinguish  members  of  this  family  as  follows : 

1.  Chiefly  herbaceous  plants. 

2.  Juice  watery,  in  many  species  acrid  and  poisonous. 

3.  Leaves   generally  compound   or   variously  cut   and 

divided,    without    true    stipules,    but    frequently 
dilated  at  the  base. 

4.  All  parts  of  the  flower  free  and  distinct.     Corolla 

oiten  wanting,     floral  envelopes  and  numerous 
stamens  hypogynous. 

5.  Carpels  numerous  or  few,  forming  achenia,  berries, 

or  follicles  in  fruit.1 

This  family  of  plants  is  of  interest  in  many  ways. 
Owing  to  their  active  properties  many  of  the  species 
such  as  gold-thread,  black  hellebore,  aconite,  larkspur,  and 
Hydrastis  are  employed  medicinally.  In  fact  these  active 
properties  constitute  an  important  feature  of  their  relation- 
ship. The  order  furnishes  a  number  of  ornamental  plants 
common  in  cultivation,  such  as  Clematis,  columbine,  monks- 
hood,  and  others.  The  color  of  the  flowers,  yellow  and 
white  in  many  of  the  simpler  species,  passing  into  red  and 
1  Cf.  Gray,  Manual,  p.  34. 


170  STUDY  OF  COMMON  PLANTS. 

blue  iii  the  more  highly  developed  ones,  taken  in  connec- 
tion with  the  striking  modifications  of  form  by  which  the 
latter  have  become  more  and  more  perfectly  adapted  to 
the  visits  of  insects,  gives  some  support  to  the  theory 
called  the  Law  of  Progressive  Coloration.1 

SPECIAL   STUDIES. 

I.   Colors  of  flowers  belonging  to  the  Ranunculacese. 

II.  Various  degrees  of  adaptation  to  fertilization  by  the 
agency  of  insects  in  this  family.  Is  self-fertiliza- 
tion possible  in  the  majority  of  cases  ?  Is  it  impos- 
sible in  any  species  ? 

III.  Fruits  of  the  Ranunculacese. 

IV.  Dissemination   of  seeds.      Special   arrangements   in 

Clematis  and  other  genera. 

1  Cf .  Grant  Allen,  Colors  of  Flowers,  pp.  17-60 ;   Miiller,  Fertiliza- 
tion of  Flowers,  pp.  88,  89. 


THE   MUSTARD  FAMILY.  171 


XXIII.    THE   MUSTARD   FAMILY.    CRUCIFER^. 

MATERIAL   REQUIRED. 

Entire  plants  of  Shepherd's-purse,  Capsella  Bursa-pastoris,  Mcench, 
with  both  flowers  and  fruit. 

Specimens  of  any  of  the  following  species  that  can  be  obtained : 
Spring  Cress,  Cardamine  rhomboidea,  DC. ;  Pepper-root,  Dentaria 
diphylla,  L. ;  Water  Cress,  Nasturtium  officinale,  11.  Br. ;  Sweet 
Alyssum,  Alyssum  maritimum.  Lam.;  Rocket,  Hesperis  matronalis, 
L. ;  Peppergrass,  Lepidium  Virginicum,  L. ;  Hedge  Mustard,  Sisym- 
brium  officinale,  Scop. ;  Wild  Mustard,  Brassica  Sinapistrum,  Boiss. 

SHEFHERD'S-FURSE.     Capsella  Bursa-pastoris,  Moench. 
Distribution. 

Record  your  own  observations  as  to  the  occurrence  arid 
habits  of  this  plant.  Does  it  manifest  a  preference  for 
any  particular  soil  or  locality  ? 

General  Characters. 

Write  an  accurate  description  of  the  root,  stem,  leaves, 
and  inflorescence. 

Flower  and  Fruit. 

I.  Study  the  plan  of  the  flower,  noting  the  number  and 
arrangement  of  sepals,  petals,  and  essential  organs.     Show 
the    application    of    the    word    "cruciform"    as    used    to 
describe  the  corolla.     Are  the  stamens  all  alike  ? 

II.  Examine  the  structure  of  the  ovary.     Compare  it  as 
it  appears  in  the  flower,  with  partially  and  fully  developed 


172  STUDY   OF   COMMON   PLANTS. 

fruits.  How  many  carpels  are  there  ?  Attachment, 
direction,  and  form  of  ovules?  Mode  of  dehiscence? 
How  is  the  fruit  to  be  classified  ? 

III.  Construct  a  diagram  of  the  flower. 

IV.  Compare  the  views  of  different  writers  regarding 
the  morphology  of  the  flower  of  Cruciferse.1 

RELATIONSHIP. 

I.  Compare  with  shepherd's-purse  such  of   the  species 
named   above  as   can   be   procured,  and   determine  what 
characters  they  exhibit  in  common.     Do  they  all  have  a 
pungent  juice?    Are  they  all  herbaceous?  "Are  the  flowers 
on  the  same  plan  ?     How  far  do  the  fruits  and  seeds  agree 
in  structure  ? 

II.  Summarize  the  results  of   your  observations  in  a 
brief  general  description  of  cruciferous  plants. 

NOTE. — To  complete  this  comparative  study  at  all  satisfactorily  will  re- 
quire much  time  and  patience.  In  studying  the  seeds  it  will  be  best  to 
obtain  those  of  different  genera  from  the  seed  store,  sow  a  part  of  them 
in  moist  sawdust,  and  dissect  carefully  from  day  to  day.  If  the  time  is 
short,  it  may  be  best  to  limit  the  comparison  to  a  very  few  species,  but 
if  even  two  or  three  genera  are  thoroughly  studied,  and  the  descriptions 
accompanied  by  floral  diagrams  and  sketches  of  the  structure  of  fruits 
and  seeds,  the  student  cannot  fail  to  be  impressed,  as  in  no  other  way, 
with  the  persistent  and  marked  features  of  this  remarkable  group  01 
plants. 

The  flowers  of  the  Cruciferse,  notwithstanding  their 
great  uniformity  of  structure,  exhibit  striking  physiologi- 
cal differences.  The  number  and  position  of  the  nectaries 
is  extremely  variable.  Some  have  a  strong  odor,  and  in  at 
least  one  species  this  is  associated  with  evening  expansion 

1  Cf.  Gray,  Structural  Botany,  pp.  206,  207  ;  Arthur,  Barnes,  and 
Coulter,  Plant  Dissection,  p.  238  (references  in  footnote). 


THE   MUSTARD   FAMILY.  173 

of  the  flower.  One  has  become  distinctly  anemophilous, 
although  giving  plain  evidence  of  having  descended  from 
entomophilous  ancestors.1 

1  Cf.  M  tiller,  Fertilization  of  Flowers,  pp.  100-114  ;    Hooker,  Nature, 
Vol.  X,  p.  134 ;  Eichler,  Bluthendiayramme,  pp.  200,  206. 


174  STUDY   OF   COMMON   PLANTS. 


XXIV.    THE    ROSE    FAMILY.     KOSACEJE. 

MATERIAL   REQUIRED. 

Flowering  shoots  of  the  cultivated  cherry,  and,  as  soon  as  they  are 
in  full  bloom,  those  of  the  peach,  plum,  apple,  and  pear. 

Representatives  of  the  following  genera,  as  far  as  they  can  be  ob- 
tained in  flower  or  fruit;  Fragaria,  Physocarpus,  Potentilla,  Geum, 
Rubus,  Rosa,  Crataegus. 

THE   CHERRY.     Prunus  Cerasus,  L. 
Distribution. 

The  cultivated  cherry  is  familiarly  known  in  the  north 
temperate  zone  of  both  hemispheres.  For  the  evidence 
regarding  the  region  to  which  it  is  indigenous,  see  De 
Candolle,  Origin  of  Cultivated  Plants,  pp.  206-210. 

Flower  and  Fruit. 

I.  Study  the  parts  of  the  flower  in  succession,  noting 
their   form  and  insertion,  the  union  of   parts,  and  other 
modifications  if  such  exist. 

II.  Make  a  longitudinal  section  and  draw  it  accurately, 
Is  any  nectar  to  be  found  ?     If  so,  are  there  any  arrange- 
ments for  its  protection  ? 

III.  Make  longitudinal  sections  of  a  number  of  ovaries 
and  transverse  ones  of  others.     Determine  the  number  of 
ovules,  their  form  and  place  of  attachment.     Draw.    Com- 
pare the  number  of  ovules  in  flowers  just  opened  and  in 
those  that  are  fading  or  have  lost  their  corolla. 


THE   ROSE  FAMILY.  175 

IV.  Construct  a  diagram  of  the  flower. 

V.  Does  the  structure  of  the  flower  present  any  adap- 
tations to  the  visits  of  insects  ? 

VI.  How  is  the  dissemination  of  seeds  provided  for  ? 


RELATIONSHIP. 

I.    With  the  cherry  compare  -first  the  cultivated  plum, 
in  flower  about  the  same  time. 

1.  Note   every   point    of    difference   between   the   two 

species,  giving  special  attention  to  the  structure 
of  the  flower. 

2.  Observe  the  points  in  which  they  agree. 

II.  Compare  the  flowers  of  the  peach  with  those  of  the 
cherry  and  plum,  noting  the  features  in  which  all  agree 
and  those  in  which  they  differ. 

III.  Examine    next  the  flowers  of   the  pear   or  apple. 
Make  a  longitudinal  section,  draw  it  and  compare  with 
that  of  the  cherry  flower.     Make  successive  cross-sections 
of  the  ovary  till  one  is  found  that  shows  the  ovules  clearly. 
Draw  and  compare  with  similar  sections  of  the  ovary  of 
the  cherry. 

IV.  Make  a  similar  study  of  the  flowers  of  the  straw- 
berry.    Indicate  all  the  points  in  which  they  differ  from 
those    of    the   cherry  and  apple.      Compare   longitudinal 
sections  of  all  three. 

V.  Having   made    a   further   comparative   study  of  as 
many  of  the  plants  of  this  family  as  are  available,  sum- 
marize the  characters  that  you  have  found  to  be  general, 
taking   leaves,    fruit,    etc.,   into    account    as  well  as    the 
flowers. 


176  STUDY   OF   COMMON   PLANTS. 

If  enough  species  have  been  examined  the  characters 
thus  derived  will  be  those  of  the  Rosacese  or  Rose  Family, 
a  large  and  important  natural  order,  furnishing  a  large 
proportion  of  the  fruits  of  the  north  temperate  zone, 
numerous  ornamental  species,  among  them  the  rose, 
spiraea,  hawthorn,  and  mountain-ash,  and  some  medicinal 
plants,  including  the  wild  cherry  and  others. 

The  flowers  of  the  various  genera  exhibit  interesting 
peculiarities  of  color  and  structure  corresponding  to  the 
different  degrees  of  adaptation  to  insect  visitors.1 

SPECIAL    STUDIES. 

I.  Development  of  a  cherry.     This  involves  a  study 

of  the  ovary  and  its  .changes  during  the  entire 
period  of  the  formation  of  the  fruit.  Sections  of 
different  specimens  should  be  made  at  frequent 
intervals,  and  a  series  of  drawings  kept  with  their 
accompanying  dates. 

II.  A  similar  study  of  the  development  of  the  apple. 

III.  How  far  the  production  of  our  domestic  fruits  is 

dependent  on  the  agency  of  insects. 

IV.  Evidence  regarding  the  4%'law  of  progressive  colora- 

tion "  drawn  from  the  flowers  of  this  family.2 

V.  Collection  and  classification  of  the  indigenous  rosa- 
ceous plants  of  the  region  in  which  the  study  is 
carried  on. 

VI.    Origin  and  varieties  of  the  cultivated  strawberry. 
VII.   Extra-floral  nectaries  and  their  use. 

1  Cf.  Miiller,  Fertilization  of  Flowers,  pp.  242,  243. 

2  Allen,  Colors  of  Flowers,  p.  25  et  seq. 


THE   PEA    FAMILY.  177 


XXV.     THE    PEA    FAMILY.     LEGUMINOS^. 

MATERIAL   REQUIRED. 

Entire  specimens  of  the  wild  lupine,  Lupinus  perennis,  L.,  in  flower. 
Flowers,  leaves,  and  fruits  of  some  or  all  of  the  following  species : 
RoUnia  Pseudacacia,  L. ;  Vicia  Caroliniana,  Walt. ;  Trifolium  pra- 
tense,  L. ;  Melilotm  alba,  Lam. ;  Lathyrus  palustris,  L. ;  Lathyrus 
odoratus,  L. 

WILD  LUPINE.     Lupinus  perennis,  L. 

Distribution  and  General  Characters. 

Note  locality  and  habits.  Is  this  species  indigenous  or 
introduced  ?  Describe  in  detail  stem,  leaf,  and  inflo- 
rescence. 

Flower. 

I.  How  many  divisions  has  the  calyx?     Is  its  surface 
smooth  or  hairy  ? 

II.  With  a  number  of  good  specimens  at  hand,  observe 
in   their  natural  position   the  parts   of   the   corolla,  their 
form,    color,    and   relations    to    each    other.      They   have 
received  special  names  that  must  be  made  familiar.     The 
conspicuous  upper  petal  is  called  the  standard,  vexillum, 
the  two  lateral  ones  are  the  wings,  alee,  while  the  two  lower 
ones  are  united  to  form  the  keel,  carina. 

III.  Examine  critically  each  of  these  parts. 

1.  Are  there  any  grooves  or  ridges  on  the  standard?     If 
so  notice  their  form  and  direction.     See  if  there 


178  STUDY   OF   COMMON    PLANTS. 

are  any  lines  or  dots  likely  to  serve  as  path 
pointers.  Compare  the  color  of  the  standard  of  a 
number  of  flowers. 

2.  Observe  the  form  and  structure  of  the  wings.  Re- 
move one  and  sketch  its  outline.  In  an  unin- 
jured flower,  notice  particularly  how  the  wings 
are  fitted  to  the  keel  and  standard. 

IV.  With  a  pencil,  or  other  instrument,  push  the  wings 
downward  with  some  force,  imitating  the  action  of  a  heavy 
insect.     Repeat  the  operation  on  different  specimens  until 
its  result  is  clearly  seen. 

V.  See  if  you  can  understand  how  it  is  that  the  wings 
and  keel  return  to  their  position  when  the  pressure  is 
removed,  and  whether  there  is  any  advantage  in  this. 

VI.  Examine  next  the  structure  and  mechanism  of  the 
essential  organs. 

1.  Remove   the  floral  envelopes  from  the  side  of  the 

flower,  leaving  the  other  parts  undisturbed.  The 
stamens  and  pistil  can  now  be  studied  to  advan- 
tage in  their  natural  position. 

2.  Count  the  stamens.     Are  they  monadelphous  or  dia- 

delphous  ?  Are  they  all  alike  ?  Compare  those 
of  flowers  about  to  open  with  younger  and  older 
ones. 

3.  Look  at  the  end  of  the  keel  of  uninjured  flowers. 

Where  is  the  pollen  stored  after  the  dehiscence 
of  the  anthers  ?  Examine  and  describe  the  mech- 
anism by  which  it  is  pushed  out  when  the  keel  is 
opened. 

4.  Observe  next  the  shape  of  the  pistil,  the  direction 

taken  by  the  style,  and  the  surface  of  the  latter  as 
seen  under  a  lens. 


THE   PEA   FAMILY.  179 

5.  Finally,  with  a  number  of  perfect  specimens  of  dif- 
ferent ages,  study  the  whole  mechanism.  Write 
a  complete  account  of  the  structure  of  the  flower 
and  the  mechanical  arrangements  favoring  cross- 
fertilization,  making  outline  sketches  whenever 
it  is  necessary  to  render  the  description  more 
intelligible.1 

RELATIONSHIP. 

As  the  flowers  of  different  plants  belonging  to  the  pea 
family  are  to  be  had,  compare  their  structure  and  mech- 
anism with  those  of  the  lupine.  Any  of  the  species 
named  above,  the  common  locust  for  example,  in  flower  a 
little  later  than  the  lupine,  will  present  interesting  points 
for  comparison. 

1.  Do  corresponding  whorls  of  the  flowers  of  different 
species  agree  as  to  position,  form,  and  number  of  parts  ? 

2.  Is  the  mechanism  by  which  fertilization  is  accom- 
plished essentially  the  same  as  in  the  lupine  ? 

3.  In  specimens  that  are  past  flowering,  study  the  fruit 
in  early  and  later  stages  of  development. 

4.  Observe  the  position  and  form  of  the  ovules,  and, 
in  older  specimens,  the  mode  of  clehiscence  of  the  fruit. 

5.  Aside  from  characters  drawn  from  flowers  and  fruit, 
determine  whether  leaves  of  the  different  species  present 
any  common  features. 

6.  Summarize  the  results  of  your  comparative  study  in 
a  brief  statement  of  the  characters  common  to  those  mem- 
bers of  the  Leguminosa3  that  you  have  become  acquainted 
with. 

1  Cf.  Miiller's  account  of  Lupinus  luteus,  the  structure  of  which  is 
much  like  that  of  Lupinus  per ennis.  Fertilization  of  Flowers,  p.  187. 


180  STUDY  OF  COMMON  PLANTS. 

The  Leguminosae  constitute  a  large  and  remarkable 
family  of  plants,  including  between  six  and  seven  thou- 
sand species,  distributed  throughout  the  world,  but  most 
abundant  in  tropical  regions.  Many  of  the  species  are  of 
economical  interest.  The  various  kinds  of  clover  furnish 
important  forage  crops,  and  peas,  beans,  and  lentils  form  an 
almost  indispensable  constituent  of  the  food  plants  of  the 
world.  Dye  woods  and  drugs  are  yielded  by  a  consider- 
able number.  Some  are  exceedingly  poisonous,  among 
them  the  famoiis  ordeal  bean  of  Calabar.  Botanically  they 
are  of  special  interest  for  the  peculiarities  of  the  mechanism 
by  which  their  flowers  are  adapted  to  cross-fertilization. 
A  large  proportion,  too,  of  plants  whose  leaves  exhibit 
"  sleep  movements  "  belong  to  this  family. 

SPECIAL    STUDIES. 

I.    Arrangements  for  cross-fertilization  in  the  Legu- 

minosse. 

II.   Extent  to  which  the  production  of   seeds  of  red 
clover  is  dependent  on  the  agency  of  insects. 

III.  Capacity  of  the  common  pea  for  self-fertilization. 

IV.  Occurrence  of   modified  leaves,   such  as    tendrils, 

phyllodes,  etc.,  among  the  Leguminosse. 
V.    Morphology  of  protective  structures  of  various  legu- 
minous plants,  e.g.  spines   of   locust  and   honey 
locust,  prickles  of  Schrankia,  and  hairs  of  Des- 
modium. 
VI.    Sleep  movements  of  clover,  lupine,  and  other  plants 

of  this  family. 

VII.    Affinities  of  the  Leguminosse. 
VIII.    Causes  of  the  wide  distribution  of  this  family. 
IX.   Varieties  of  cultivated  peas  and  beans. 


THE   GERANIUM   FAMILY.  181 


XXVI.    GERANIUM    FAMILY.    GERANIACE^E. 

MATERIAL   REQUIRED. 

Specimens  of  horseshoe  geranium,  Pelargonium  zonale,  L.,  in  flower. 
Wild  cranesbill,  Geranium   maculatum,    L. ;    Nasturtium,    Tropceolum 

majus,   L. ;    Touch-me-not,   Impatiens  fulva,  Nutt.,  or  cultivated 

balsams  that  have  not  become  double. 

HORSESHOE   GERANIUM.     Pelargonium  zonale,  L. 

Distribution. 

The  "horseshoe  geranium"  is  universally  cultivated. 
In  common  with  various  other  cultivated  species  of  the 
same  genus,  it  is  indigenous  to  southern  Africa.  Very 
many  varieties  have  been  produced. 

General  Characters. 

With  good  specimens,  observe  and  describe  the  various 
external  features,  such  as 

I.    Mode  of  branching. 
II.    Leaf  arrangement. 

III.  Presence  or  absence  of  stipules. 

IV.  Form  of  leaves. 

Inflorescence. 

Taking  care  to  select  plants  the  flowers  of  which  have 
not  become  double,  compare  inflorescences  of  different 
ages,  and  ascertain  the  order  of  development  of  the  flowers. 


182  STUDY    OF   COMMON   PLANTS. 

NOTE.  —  Like  many  other  facts  usually  treated  as  morphological,  the 
character  of  the  inflorescence  is  of  much  physiological  importance. 
The  successive  opening  of  the  flowers  in  regular  order,  instead  of  simul- 
taneously, insures  a  much  longer  period  of  time  during  which  fertilization 
may  take  place,  and  their  position  and  aspect  when  ready  for  pollination 
are  most  frequently  such  as  to  render  them  conspicuous  and  easily  acces- 
sible to  insect  visitors.  The  latter,  while  gathering  honey,  are  often 
observed  to  proceed  in  a  methodical  manner  corresponding  to  the  order 
of  development  of  the  flowers. 

Flower. 

I.  Study  the  structure  and  plan  of  the  flower.     Is  it 
perfectly  regular  ? 

NOTE.  —  Give  special  attention  to  this  point.  The  beginnings  of  irregu- 
larity are  of  great  interest,  since  they  give  us  a  clue  to  the  way  in  which 
some  of  the  most  efficient  mechanical  contrivances  in  the  vegetable  king- 
dom have  originated. 

II.  Study  next  the  ovary. 

1.  Cut  transverse  and  longitudinal  sections  of  ovaries  of 

various  ages. 

2.  Make  out  the  form  and  place  of  attachment  of  the 

ovules. 

3.  In  the  partially  developed  fruit  examine  the  imma- 

ture seeds,  and  note  the  form  and  position  of  the 
embryo,  easily  recognized  by  its  green  color. 

4.  Construct  a  diagram  of  the  flower. 

Physiological  adaptations. 

I.  Examine  with  a  good  lens  the  surface  of  stem,  leaves, 
flower-stalk,  and  calyx.     Are  there  any  distinctively  pro- 
tective arrangements  ? 

II.  In  what  ways  is  the  inflorescence  adapted  to  cross- 
fertilization  ?     Notice  the  position  of  the  open  flowers  as 
contrasted  with  that  of  the  flower  buds.     Effect  of  "  mass- 
ing." 


THE   (GERANIUM   FAMILY.  183 

III.  Study  the  flower  itself  with  reference  to  the  same 
question.     Compare  the  color  of  different  specimens  and 
varieties.     Is  there  anything  to  indicate  to  a  visiting  insect 
the  way  to  the  nectar  ?     Find  the  nectar-tube  and  explore 
with  a  bristle. 

NOTE.  —  Some  specimens  have  a  nectar-tube  united  with  the  pedicel 
and  easily  recognizable  on  the  outside,  either  by  its  color  or  by  its  form- 
ing a  longitudinal  ridge.  In  others  it  is  not  readily  found.  Even  flowers 
of  the  same  inflorescence  differ  in  this  respect. 

IV.  Compare  the  stigmas  of  older  flowers  with  those  in 
which  the  anthers  are  just  shedding  their  pollen.     Are  the 
flowers  proterandrous  or  proterogynous  ? 1 

V.  Study  the  structure  of  the  mature  fruit,  and  ascer- 
tain how  the  seeds  are  disseminated. 

NOTE.  —  The  geranium  lends  itself  readily  to  experiments  in  cross- 
fertilization,  and  the  student  who  has  opportunity  is  advised  to  cross  two 
widely  different  varieties  and  compare  the  growth  and  vigor  of  the  crossed 
seedlings  with  that  of  seedlings  derived  from  self-fertilized  flowers. 
Read  the  chapter  on  Pollination  in  Professor  L.  H.  Bailey's  Nursery  Book. 


RELATIONSHIP. 

I.  Compare  the  plant  just  studied  with  the  wild  cranes- 
bill,  noting  points  of  agreement  and  difference.  Give 
special  attention  to  the  flowers  of  the  two  genera,  examin- 
ing them  whorl  by  whorl,  until  you  are  satisfied  regarding 
their  differences.  Record  these  in  detail.  Refer  in  this 
connection  to  Miiller's2  or  Lubbock's3  account  of  various 
species  of  Geranium. 

1  Cf.  Darwin,  Cross-  and  Self-fertilization  in  the  Vegetable  Kingdom, 
p.  142. 

2  Fertilization  of  Flowers,  pp.  149-158. 

8  British  Wild  Flowers  in  Eelation  to  Insects,  pp.  43,  44,  72-74. 


184  STUDY   OF   COMMON   PLANTS. 

II.  Compare  next  the  cultivated  nasturtium,  Tropceolum 
majus,  L.,  with  the  horseshoe  geranium. 

1.  Note  the  very  different  habits  of  the  plant,  the  pecu- 

liarities of  its  foliage  leaves,  and  means  of  pro- 
tection. 

2.  Observe  the  structure  and  plan  of  the  flower.     Note 

particularly  the  color  of  both  calyx  and  corolla, 
the  guiding  lines,  nectar-tube,  mode  of  guarding 
the  entrance  to  the  latter,  dichogamy,  structure 
of  ovary,  and  number  of  carpels.1 

III.  In  addition  to  the  foregoing,  study  if  possible  one 
or  more  indigenous  species  of  Impatiens,  or  forms  of  the 
cultivated  "  balsam  "  that  have  not  become  double.     They 
are  of  special  interest  as  regards  both  the  peculiar  modi- 
fications of  the  flower  and  the  mechanism  of  seed  dissemi- 
nation. 

1.  Comparing  the  plan  of  the  flower  with  that  of  the 

species  previously  studied,  try  to  ascertain  whether 
there  has  been  consolidation  or  suppression  of 
parts,  or  both. 

2.  Does  the  structure  imply  adaptation  'to  cross-ferti- 

lization?    Does  dichogamy  exist? 

3.  If  opportunity  permits,  observe  what  visitors  Impati- 

ens has  and  their  mode  of  operation. 

4.  Examine  ripe  fruits  and  investigate  the  mechanism 

of  seed  dissemination.  Is  it  the  same  in  principle 
as  in  Pelargonium  and  Geranium?2 

NOTE.  — "  The  relationship   of  Pelargonium    with    the    closely 
allied  genus  Geranium  is   obvious,  but  it  differs  in  important 

1  Cf.  Lubbock,  I.e.,  pp.  75,  76. 

2  Cf.  Duehartre,  Elements  de  Botanique,  p.  791. 


THE  GERANIUM  FAMILY.  185 

particulars  from  Tropaeolum  and  Impatiens,  both  of  which,  in 
recognition  of  their  wide  departure  from  more  primitive  forms, 
are  now  placed  in  separate  families.  The  study  of  such  a  series 
of  forms  is  in  the  highest  degree  instructive,  presenting  as  it 
does  very  important  evidence  regarding  the  descent  of  these 
peculiarly  modified  genera. 


186  STUDY   OF  COMMON   PLANTS. 


XXVII.    THE  SPURGE   FAMILY. 
EUPHORBIACEJE. 

MATERIAL   REQUIRED. 

Spurge,  Euphorbia  Cyparissias,  L.,  and  other  species  of  Euphorbia. 
Representatives  of  other  genera  of  the  same  family  as  far  as  these 
are  procurable. 

SPURGE.     Euphorbia  Cyparissias,  L. 
Distribution. 

In  what  situation  is  this  plant  usually  found  growing  ? 
Have  you  observed  anything  as  to  its  persistence  from 
year  to  year,  where  it  has  once  become  established  ?  Do 
its  habits  indicate  that  it  is  an  indigenous  species  ? 

General  Characters. 

Study  the  general  features  of  the  plant  and  write  a  brief 
description.  In  addition  to  the  ordinary  botanical  char- 
acters note  particularly 

1.  The  way  in  which  new  shoots  arise. 

2.  The  abundant  latex  in  every  part.1 

3.  The   great  variety    of    foliar  organs  —  scale  leaves, 
foliage  leaves,  and  floral  leaves  —  and  their  form,  position, 
and  color. 

Inflorescence  and  Flowers. 

The  morphology  of  the  flower  in  this  family  has  been 
the  subject  of  much  discussion  and  an  extended  literature. 

1  Care  should  be  exercised  in  handling  spurges  as  the  juice  is  poisonous. 


THE   SPURGE   FAMILY.  187 

Without  attempting  at  the  outset  a  critical  theoretical 
study,  we  shall  simply  undertake  to  observe  the  floral 
organs  as  they  are,  and  give  to  them  their  commonly 
accepted  names.  Book  descriptions  and  figures  are  best 
left  alone  until  the  plant  has  been  studied  at  first  hand. 

I.  Observe  first  the  general  arrangement  of  the  inflores- 
cences.    They  are  borne  on  long  slender  stalks  that  arise 
close  together  near  the  apex   of   the  stem,  and   present 
collectively  the  general  appearance  of  an   umbel.     Is  it 
strictly  an  umbel  ? 

II.  The  slender  stalks  each  bear  near  their  extremity  a 
pair  of  heart-shaped,  yellowish,  floral  leaves.     Notice  care- 
fully what  there  is  above  the  floral  leaves.     Compare  a 
number  of  specimens  of  different  ages.     Do  you  find  still 
other  floral  leaves?     If  so,  do  they  resemble  the  first  pair 
in  shape  and  color  ?     Floral  leaves  of  the  second  and  third 
order  are  of  common  occurrence.     Do  you  find  any  of  a 
higher  order? 

III.  Having  found  all  the  floral  leaves,  we  come  to  the 
inflorescence  proper.     It  greatly  resembles  a  small  flower, 
and  was  described  as  such  by  some  of  the  older  botanists. 
The  cup-shaped  structure  that  looks  like  a  calyx  is  really 
an  involucre.      Notice  the  four  "crescent-shaped  glands" 
and  their  position  on  the  involucre. 

IV.  Remove  enough   of   the    involucre   to  expose  the 
small  flowers  within.     Do  this  with  several  specimens  of 
different  ages.     With  a  lens,  examine  the  minute  staminate 
flowers.     Note  their  position  and  number,  the  form  of  the 
anther,   and  the  point  where  the  short  filament  is  con- 
nected with  the  long   pedicel.     (Each   staminate    flower 
consists    of    a    single    stamen,    mounted    on    a    distinct 
pedicel.) 


188  STUDY   OF    COMMON   PLANTS. 

V.  The  single  pistillate  flower  is  far  more  conspicuous 
than  the  staminate  ones.     As  the  ovary  develops  it  pro- 
trudes beyond  the  involucre,  so  that  the  entire  flower  is 
easily  studied.     Observe 

1.  The  form  of  the  ovary. 

2.  The  number  of  styles  and  stigmas. 

3.  The  number  of  cells  in  the  ovary,  as  seen  in  cross- 

section,   and    the    number    and    position   of    the 
ovules. 

VI.  With  a  number  of  entire  plants  review  all  that  we 
have  learned  about  the  species.     See  that  all  the  facts  are 
clearly  in  mind,  and  that  you  are  able  to  designate  each 
part  by  its  proper  name.     Do  you  consider  the  plant  well 
adapted  to*  survive  in  the  struggle  for  existence  ?     If  so, 
show  how. 

RELATIONSHIP. 

With  the  species  already  studied  compare  other  mem- 
bers of  the  genus  such  as  Euphorbia  corollata,  L.,  E. 
marginata,  Pursh,  E.  maculata,  L.,  and  one  or  more  repre- 
sentatives of  other  genera,  as,  for  example,  Acalypha 
Virginica,  L.,  and  the  cultivated  castor-oil  plant,  Ricinus 
communis,  L.  (The  seeds  of  the  latter  are  of  large  size, 
and  are  more  easily  studied  than  those  of  the  spurge.) 

Having  compared  as  many  species  as  practicable,  see 
how  far  the  characters  you  have  found  to  be  common 
to  all  agree  with  the  family  characters  as  given  in  the 
manuals. 

Euphorbia  Cyparissias  is  a  familiar  representative  of  a 
large  and  peculiar  family  of  plants.  It  is  found  in  patches 
by  roadsides  and  old  dwellings  where  it  has  escaped  from 
cultivation.  Its  copious  milky  juice,  narrow  leaves,  and 
tufted  habit  have  given  it  the  common  name  of  "  milk- 


THE   SPtJRGE   FAMILY.  •        189 

moss,"  in  addition  to .  that  of  "  spurge,"  which  it  shares 
with  numerous  other  species  of  the  same  genus.  The 
family  to  which  it  belongs  is  chiefly  tropical,  and  is  one 
of  the  few  that  are  specially  distinguished  by  their  poison- 
ous properties.  Cases  of  poisoning  as  a  result  of  handling 
species  cultivated  for  ornament  are  not  infrequent.  It 
includes  a  number  of  species  with  powerful  medicinal 
properties,  and  others  that  furnish  valuable  food  products, 
while  the  fleshy  Euphorbias,  the  Poinsettia,  and  others, 
are  well-known  ornamental  plants. 


190  STUDY  OF  COMMON  PLANTS. 


XXVIII.    THE   MAPLE   FAMILY.     ACERACEJE. 

MATERIAL '  REQUIRED. 

Flowers  of  the  different  species  of  maples  as  they  open  in  the  spring. 
Fruits  of  the  sugar  maple  gathered  after  they  have  fallen  from  the 

trees  in  the  autumn.    Fruits  of  the  red  and  silver  maples  gathered 

in  the  summer. 
Leaves  of  all  the  species.     Either  fresh  or  pressed  specimens  of  the 

latter  will  serve. 

Flowers. 

The  flowers  of  the  red  maple  open  early  in  the  spring 
arid  may  be  taken  first.  Specimens  should  be  gathered 
from  a  number  of  trees  so  as  to  have  the  different  forms  of 
flowers  for  comparison. 

I.  Observe  the  position  of  the  flower  bud  and  the  color 
and  position  of  the  bud-scales. 

II.  Compare    the    flowers    of    different    trees.      Select 
first,  for   critical   study,  those   that   have   well-developed 
stamens. 

1.  How  many  divisions  of  the  calyx  are  there?     Of  the 

corolla  ? 

2.  Is  this  number  the  same  in  all  the  specimens  ?    Does 

it  correspond  with  the  number  of  stamens  ? 

3.  How  are  the  stamens  inserted  ? 

4.  Is  there  a  pistil  ? 

5.  Are  there  any  organs  for  the  secretion  of  nectar? 


THE   MAPLE   FAMILY.  191 

III.  Next    take   specimens    that    have   well-developed 
pistils. 

1.  Are  stamens  present?     If  so,  how  do  they  compare 

with  those  of  the  flowers  previously  studied  ? 

2.  Are  the  floral  envelopes  alike  in  all  the  flowers? 

3.  Notice  the  form  and  structure  of   the  pistil.     How 

many  carpels   are    there?      How  many  ovules  in 
each  cell  ? 

IV.  Compare  with  these  the  flowers  of  the  silver  maple, 
noting  carefully  all  the  points  of  likeness  and  difference. 

1.  Are  petals  present? 

2.  Do  .all  the  flowers  have  both  stamens  and  pistils? 

3.  Is  the  ovary  smooth  or  hairy  ? 

4.  Does   it   agree   in    structure    with   that  of   the   red 

maple  ? 

5.  Do  different  specimens  exhibit  any  variation    as  to 

the  number  of  carpels  ? 

V.  Compare  flowers  of   the  sugar   maple,  which   open 
some  days  later,  with  those  of  the  red  and  silver  maples. 

1.  Are  there  any  differences  as  regards 

a.  Form  and  position  of  the  flower  clusters  ? 

b.  Color  of  the  calyx  ? 

c.  Structure  of  the  essential  organs? 

2.  Are  all  the  flowers  of  the  same  tree  alike  ?     How  is 

it  with  those  of  the  red  and  silver  maples  in  this 
respect  ? 

The   maples   are    described    as  being  "  polygamo-dice- 
cious."    What  is  meant  by  this  ?    Do  you  find  that 
the  facts  correspond  with  the  statement? 
Fruits. 

Study  next  fruits,  taking  first  those  of  the  sugar  maple 
gathered  the  preceding  fall. 


192  STUDY   OF   COMMON   PLANTS. 

With  the  fruits  of  the  sugar  maple,  compare  those  of 
the  red  and  silver  maples,  noting  all  the  external  and 
structural  differences  by  which  they  may  be  distinguished. 

Leaves. 

Compare -the  leaves  of  all  three  kinds  until  you  are  able 
to  distinguish  the  species  at  sight  by  means  of  the  leaves 
alone. 

Finally  review  the  observations  made  thus  far,  see  if 
anything  is  to  be  added,  and  write  a  complete  account 
of  the  characters  common  to  all  three  species  and  also  of 

those  peculiar  to  each. 

* 

SPECIAL   STUDIES. 

I.  Critical  comparison  of  the  Box-elder,  Negundo 
aceroides,  Mcench.,  with  the  maples.  Does  it  have 
the  essential  characters  of  a  maple  ? 

II.    Polygamous  plants.    Cf.  Darwin,  Different  Forms  of 
Flowers  on  Plants  of  the  Same  Species,  Chap.  VII. 


THE  MALLOW   FAMILY.  193 


XXIX.    THE    MALLOW    FAMILY.    MALVACEAE. 

MATERIAL   REQUIRED. 

Common  mallow,  Malva  rotundifolia,  L.,  in  flower  and  fruit. 

Other  representatives  of  the  family,  such  as  Hollyhock,  Althcea  rosea, 
Cav. ;  Shrubby  althaea,  Hibiscus  Syriacus,  L. ;  Musk  mallow, 
Malva  moschata,  L. ;  Velvet-leaf,  Abutilon  Avicennce,  Gaertn. 

COMMON   MALLOW.     Malva  rotundifolia,  L. 
Distribution. 

In  what  situation  is  this  plant  generally  found  ?  Have 
you  any  evidence  as  to  whether  it  is  an  indigenous  or 
introduced  species  ? 

General  Characters. 

I.  Study  first  the  habits  of  the  plant  and  note  its  char- 
acteristic features. 

1.  The  strong  taproot. 

2.  Position  and  direction  of  the  numerous  branches. 

3.  Presence  or  absence  of  stipules. 

4.  Form  and  venation  of  leaves. 

5.  Position  and  character  of  inflorescence. 

6.  The  remarkably  strong  bast  fibers. 

7'.    Mucilaginous  contents,  particularly  of  the  fruits. 

II.  Enumerate  any  advantages  that  this  plant  possesses 
in  competition  with  others.  Is  it  easily  eradicated?  Why? 
Is  it  attractive  to  grazing  animals  ? 


194  STUDY   OF  COMMON  PLANTS. 

Flower. 

I.  Examine  the  flower  in  various  stages  of  development. 
Note 

1.  The  plan  of  the  flower  and  how  modified. 

2.  The  three-leaved  involucel,  "like  an  outer  calyx." 

3.  Insertion  of  the  corolla  and  the  relation  of  the  latter 

to  the  stamen-tube  (best  seen  on  longitudinal  sec- 
tion). 

4.  The  monadelphous  stamens. 

5.  Form  and  mode  of  dehiscence  of  anthers. 

6.  Number  of  stigmas.     Does  this  correspond  with  the 

number  of  divisions  of  the  ovary? 

II.  Ascertain  whether  there  are  any  adaptations  favor- 
ing cross-fertilization,  or  any  that  render  self-fertilization 
impossible. 

1.  Are  there  any  guiding  lines? 

2.  Is  nectar  produced?     If  so,  is  it  protected  in  any 

way? 

3.  Compare   flowers   of   different    ages    and    ascertain 

whether  dichogamy  exists.1 

Fruit  and  Seed. 

I.  Examine  the  fruit,  making  both  transverse  and  longi- 
tudinal sections  of  specimens  of  different  ages.  Ascertain 

1.  The  number  of  carpels. 

2.  Form  and  place  of  attachment  of  the  ovules. 

3.  Structure    and   position   of   the  embryo.      (This   is 

easily  made  out  with  a  lens  by  means  of  repeated 
sections,  trying  different  specimens  until  the  most 
favorable  ones  are  found.) 

1  Lubbock,  British  Wild  Flowers  in  Relation  to  Insects,  p.  41  ;  Miiller, 
Fertilization  of  Flowers,  pp.  142, 143. 


THE   MALLOW   FAMILY.  195 

II.  Ascertain  approximately  the  number  of  seeds  pro- 
duced by  a  single  strong  plant. 

RELATIONSHIP. 

Compare  with  the  common  mallow  at  least  one,  and  if 
possible  several,  of  the  plants  named  above,  noting  the 
various  points  of  difference  and  likeness.  Write  a  brief 
summary  of  the  characters  common  to  them  all. 

The  Malvaceae  exhibit  a  number  of  interesting  peculiari- 
ties, some  of  which  indicate  relationship  with  several  other 
families,  among  them  the  Tiliacese.  They  are  widely  dis- 
tributed in  both  hemispheres,  but  with  a  preference  for 
the  warmer  parts  of  the  globe.  The  cotton  plant  is  the 
most  important  member  of  the  family,  from  an  economical 
standpoint.  A  few  species  are  of  medicinal  value,  and  a 
considerable  number,  as  Althaea,  Hibiscus,  Abutilon,  and 
others,  are  well-known  ornamental  plants. 


196  STUDY   OF  COMMON  PLANTS. 


XXX.    THE   VIOLET   FAMILY.    VIOLACEJE. 

MATERIAL   REQUIRED. 

Specimens  of  the  cultivated  pansy  in  flower.     Indigenous  species  of 
violets. 

Flower. 

Our  study  in  the  present  case  will  be  restricted  to  the 
flower,  taking  first  that  of  the  pansy. 

I.  Compare  several  good  specimens  as  to  size  and  color, 
and  observe  how  far* they  agree. 

II.  Study  the  external  features  of  the  flower  in  order. 
Note  the  number  of  parts  in  each  whorl,  and  their  peculiari- 
ties of  form,  structure,  and  position. 

1.  Form   of    the  sepals.      Aside   from   their  size   and 

position  are  they  readily  distinguished  from  foliage 
leaves  ? 

2.  Peculiarities  of  the  corolla.     To  which  of  the  petals 

does  the  spur  belong  ?  Cut  into  it  and  see  whether 
it  contains  anything  likely  to  be  of  use  to  the 
flower.  What  do  you  conclude  as  to  its  function  ? 

3.  Study  the  disposition  of  colors.     Compare  as  many 

specimens  as  practicable.  Where  do  the  "  guiding 
lines  "  converge  ? 

4.  Examine    the    center   of    the    flower   with   a   lens. 

Notice  the  thick  brush  of  hairs  on  either  side. 
The  position  of  the  essential  organs,  partially 
visible  farther  in. 


THE    VIOLET   FAMILY.  197 

III.  Remove  carefully  the  floral  envelopes  on  one  side 
so  as   to  expose  the  essential  organs  without  disturbing 
them.     Notice  the  relative  position  of  stamens  and  pistil, 
and   their  structural    peculiarities.      The   large,    rounded 
stigma  with  an  orifice  in  front.     The  "  lip  "  forming  the 
lower  edge  of.  this  orifice.     The  syngenesious  anthers  arid 
their  membranaceous  connectives  united  into    a  tube  just 
back  of  the  stigma.     The  two  nectaries  projecting  into  the 
spur.     The  narrow  canal  lined  with  hairs  leading  from  the 
entrance  of  the  corolla  back  to  the  spur. 

Jar  the  btamens  and  see  where  the  pollen  falls  out  and 
where  it  lodges. 

IV.  Go  over  all  the  structures  again,  in  more  than  one 
specimen,  and  see  if  you  can  determine  the  use  of  each 
part  of  the  mechanism.     Imitate  the  action  of  a   bee  by 
inserting  a  slender  piece  of  quill  or  wood,  pushing  along 
the  groove  down  to  the  nectar  cavity.     Withdraw  it  and 
see  if  it  brings  away  any  pollen.     Insert  it  into   another 
flower  and  examine  the  stigma  of  the  latter  with  a   lens 
before  and  after  the  operation  to  see  if  any  pollen  has  been 
left  on  it.1 

V.  Make  a  true  longitudinal  section  of  the  flower  (a 
razor  is  best  for  this  purpose),  and  sketch  the  parts  in  out- 
line  so  as  to  show  their   relative    position.     Name    and 
locate  each,  using  letters  and  guiding  lines. 

VI.  Make  a  transverse  section  of  the  ovary  and  examine 
under  a  lens.     Note 

1.  The  number  of  placentae. 

2,  Number,  direction,  and  form  of  ovules.      If  practi- 

cable, compare  ripe  capsules. 

1  Cf .  Sachs,  Physiology  of  Plants,  p.  795. 


198  STUDY   OF   COMMON   PLANTS. 

VII.  Construct   a   diagram    of   the    flower.      In   what 
respects  does  the  pansy  differ  from  a  "typical  flower," 
as  described  by  Gray,  Lessons,  pp.  81,  82  ? 

VIII.  Write  a  full  description  of  the  pansy. 

NOTE. — It  is  hardly  necessary  at  this  stage  of  the  student's  progress 
to  remind  him  that  a  description  of  such  a  flower  involves  much  more 
than  an  enumeration  of  the  parts  of  each  whorl,  with  an  account  of 
their  surface,  outline,  etc.  An  appreciation  of  the  marvelous  beauty  and 
exquisite  adaptations  here  displayed,  and  a  scientific  temper  that  seeks 
to  know  how  all  this  has  come  to  be  as  it  is,  will  hardly  be  satisfied  with 
mechanically  filling  the  blanks  of  some  "plant  analysis."  Write  as 
though  your  account  were  to  stand  as  the  only  written  description  of 
the  result  of  a  long  series  of  natural  experiments,  of  which  we  now  see 
the  culmination  in  a  perfect  piece  of  mechanism. 

IX.  Consult   the   references   already  given   and   those 
named  under  "  Special  Studies  "  below. 

RELATIONSHIP. 

As  the  flowers  of  various  indigenous  species  appear  in 
spring,  e.g.  Viola  palmata,  L.,  V.  pedata,  L.,  V.  pubescens, 
Ait.,  etc.,  compare  them  with  the  pansy,  and  note  the  char- 
acters common  to  them  all.  If  the  green  violet,  Solea  con- 
color,  Ging.,  is  to  be  had,  compare  this  with  the  true  violets. 

Summarize  briefly  the  points  in  which  all  these  agree. 

SPECIAL   STUDIES. 

I.  Observation  of  various  insects  that  visit  the  pansy. 
Miiller,  Fertilization  of  Flowers,  p.  118,  gives  an 
interesting  account  of  the  habits  of  different  bees. 
II.  Advantages  of  crossed  over  self-fertilized  pansies. 
See  Darwin's  experiments,  Cross-  and  Self-fertili- 
zation in  the  Vegetable  Kingdom,  pp.  123-128,  286, 
296,  304. 


THE   VIOLET   FAMILY,,  199 

III.  Variation  as  seen  in  the  cultivated  pansy.     Obser- 

vations of  differences  of  size,  shades,  and  distri- 
bution of  color  and  other  peculiarities,  even  if 
restricted  to  the  pansies  grown  in  a  single  town, 
give  a  vivid  impression  of  the  extraordinary  capac- 
ity for  variation  and  the  equally  remarkable  per- 
sistence of  essential  features  exhibited  by  this 
species. 

IV.  Dissemination  of  seeds  by  different  species  of  violets. 

See  Lubbock,  Flowers,  Fruits,  and  Leaves,  p.  54 
et  seq. 

V.  Cleistogamic  flowers.  See  Darwin,  Different  Forms 
of  Flowers  on  Plants  of  the  Same  Species,  Chap. 
VIII. 


200  STUDY    OF   COMMON    PLANTS. 


XXXI.    THE   EVENING-PRIMROSE   FAMILY. 
ONAGRACEJE. 

MATERIAL    REQUIRED. 

Evening  primrose,  CEnothera  biennis,  L.,  in  flower. 

Fire-weed,  Epilobium   angwlifolium,  L.,   Enchanter's-nightshade,  Cir- 

ccea  Lutetiana,  L.,  and  other  representatives  of  the  family,  such 

as  the  cultivated  Fuchsia. 

EVENING   PRIMROSE.     CEnothera  biennis,  L. 
Distribution. 

Where  were  the  specimens  obtained?  In  what  other 
places  in  this  country  have  you  seen  it  growing?  Does 
it  grow  in  any  other  parts  of  the  world  ? 1 

Flower. 

I.  Examine  the  whorls  in  order  and  draw  a  diagram  of 
the  flower.     Cut  a  true  longitudinal  section,  study  care- 
fully the  relation  of  the  parts,  and  draw. 

II.  Note  particularly  the  very  long  calyx-tube,  insertion 
of   petals  and   stamens,   the   versatile    anthers,   elongated 
style,  and  four  thickened  divisions  of  the  stigma. 

III.  Taking  specimens  past  flowering,  cut  transverse 
and  longitudinal  sections  of  the  ovary,  and  observe  under  a 
lens  the  number  of  rows  of  ovules  in  each  cell,  and  their 
form  and  direction. 

1  Cf.  Lubbock,  British  Wild  Flowers  in  Relation,  to  Insects,  p.  93. 


THE   EVENING-PRIMROSE   FAMILY.  201 

IV.  Using  still  older  specimens,  observe  and  describe 
the  structure  of  the  fruit  and  its  mode  of  dehiscence. 

Physiological  Adaptations. 

If  possible,  visit  both  in  the  daytime  and  evening  the 
place  where  the  plant  is  growing,  and  study  its  habits. 
Ascertain  when  the  flower  opens,  whether  its  color  and 
odor  are  attractive  to  any  particular  class  of  insects,  and 
whether  the  length  of  the  calyx-tube  or  any  other  struc- 
tural features  indicate  special  adaptations.  Endeavor  to 
ascertain  by  direct  observation  how  pollination  is  effected. 
Accounts  of  this,  so  far,  are  very  meager,  but  suggest  a 
curious  keeping  in  tow  of  two  or  more  different  sorts  of 
visitors,  some  of  them  coming  by  day  and  others  by  night.1 

RELATIONSHIP. 

I.  Obtain  specimens  of  the  great  willow-herb,  or  fire- 
weed,  Epilobium  angustifolium,  L.,  often  very  abundant  on 
newly  cleared  land  that  has  been  burnt  over,  and  compare 
the  plant  throughout  with  what  you  have  seen  of  the 
evening  primrose.  Note 

1.  Habits  and  external  characters. 

2.  Structure  of  the  flower,  especially  its  plan  and  the 

relation  of  the  various  whorls  to  each  other. 

3.  Adaptations  to  insect  visitors.     Observe  particularly 

the  position  of  the  style  in  flowers  of  different 
ages,  and  the  time  when  the  stigmas  open.  Is  this 
before  or  after  the  anthers  have  shed  their  pollen  ? 

NOTE.  — This  species  furnishes  an  excellent  example  of  proterandrous 
dichogamy.'2 

1  Cf .  Lubbock,  I.e.  ;   Miiller,  Fertilization  of  Flowers,  p.  264. 

2  Cf.  Gray,  Structural  Botany,  p.  222. 


202  STUDY   OF   COMMON   PLANTS. 

II.  Compare  the  enchanter's-nightshade  (Circcea  Luteti- 
ana,  L.),  also  in  flower  in  midsummer,  with  the  evening 
primrose. 

1.  Construct  a  diagram  of  the  flower  and  observe  how 

it  differs  from  that  of  the  latter  species. 

2.  Examine  the  flower  under  a  lens  and  observe 

a.  The  conspicuous  nectary.     (Abundant  nectar  may 

also  be  found  in  some  flowers.) 

b.  The  surface  of  the  ovary.     Can  you  suggest  more 

than  one  use  of  the  hooked  bristles  with  which 
it  is  covered  ? 

3.  Observe,  if  practicable,  the  way  in  which  pollination 

takes  place.1 

III.  A  study  of  the  cultivated  Fuchsia  may  be  made  at 
any  time  during  several  months  of  the  year,  and  if  more 
convenient  may  be  taken  as  the  type  instead  of  the  even- 
ing primrose. 

IV.  Compare  your  observations  of  the  various  members 
of  the  family  that  you  have  obtained  for  study,  and  note 
the  morphological  characters  common  to  them  all. 

iCf.  Muller,  I.e.,  pp.  266,267. 


THE  PARSLEY   FAMILY.  203 


XXXII.    THE    PARSLEY    FAMILY. 
UMBELLIFER^E. 

MATERIAL   REQUIRED. 

Harbinger-of-spring,  Erigenia  bulbosa,  Nutt.,  in  flower. 

Later  in  the  season,  representatives  of  other  genera,  such  as  Osmor- 

rhiza,  Heracleura,  Pastinaca,  Thaspium,  Daucus,  Cicuta. 
Fruits  of  fennel,  Fceniculum  vulgare,  Gsertn.,  dill,  Anethum graveolens,  L., 

and  coriander,   Coriandrum  satiuum,  L.    (to   be   procured   at  the 

drug  store). 

HARBINGER-OF-SPRING.     Erigenia  bulbosa,  Nutt. 
Distribution  and  General  Characters. 

I.  Record  what  you  have  noticed  as  to  the  habitat  of 
this  species.     Does  it  appear  to  be  indigenous  or  intro- 
duced ? 

II.  With  perfect  specimens  at  hand,  study  the  general 
features  of  the  plant,  noting  particularly 

1.  The  underground  stem.     Describe  its  form  and  struct- 

ure.     As  a  modified  stem  how  is  it  to  be  classi- 
fied?1 

2.  The  habit  of  the  plant  as   regards  size,  branching, 

arid  any  other  feature  that  appears  to  be  charac- 
teristic. 

3.  Leaves.     Compare  a  number  of  proper  foliage  leaves 

and  describe  one  that  you  regard  as  typical.   Notice 

a.  The  expanded,  sheathing  petiole. 

b.  The  extent  to  which  the  leaf  is  compound. 

1  Cf,  Gray,  Lessons,  p.  42  et  seq. 


204  STUDY   OF  COMMON   PLANTS. 

c.  The  uppermost  leaves.  Those  subtending  a  group 
of  inflorescences  constitute  an  involucre,  those 
subtending  each  separate  inflorescence  an  in- 
volucel.  Do  the  leaves  of  involucre  and  involu- 
cel  differ  in  any  important  particular  from  the 
lower  leaves  ? 

4.    The  character  of  the  inflorescence,  and  the  grouping 
of  several  inflorescences  to  form  a  compound  umbel. 

Flower. 

I.  Examine  different  flowers  until  you  are  satisfied  as  to 
what  parts  are  present.     Note  the  essential  facts  of  form, 
number,  position,  etc. 

II.  Write  a  description,  and  indicate  all  the  points  in 
which  this  differs  from  a  "  typical  flower." 

NOTE. —  In  this  family  the  inflorescence  and  flowers  are  particularly 
characteristic ;  it  is  important,  therefore,  that  their  distinctive  features 
should  be  impressed  on  the  mind  before  proceeding  farther. 

Fruit. 

Fully  mature  specimens  are  indispensable  in  studying 
the  fruit  of  any  member  of  this  family ;  accordingly, 
instead  of  waiting  for  the  Erigeriia  to  ripen,  it  will  be  con- 
venient to  take  commercial  specimens  of  fennel,  coriander, 
and  dill,  which  will  serve  as  good  representatives  of  the 
fruits  of  umbelliferous  plants.  Moreover,  by  studying 
several  kinds,  instead  of  one,  we  shall  gain  a  clearer  im- 
pression of  their  really  characteristic  features. 

I.  Observe  carefully  the  external  features  of  the  three 
fruits.  That  of  the  coriander  is  globular,  fennel  is  more 
nearly  cylindrical,  while  dill  is  much  flattened.  In  spite, 
however,  of  these  marked  differences,  there  are  a  number 
of  characters  common  to  all  three.  Note 


THE   PARSLEY   FAMILY.  205 

1.  The  ready  splitting  of   the  fruit   into   two  halves, 

mericarps. 

2.  The  strongly  marked  longitudinal  ribs  on  the  outer 

surface  of  each  mericarp. 

3.  The  stylopodium,  a  short  conical  body  in  which  the 

fruit  is  prolonged  above. 

4.  The  carpophore,  or  prolongation  of  the  pedicel ;  its 

two  thread-like  branches  each  supporting  one  of 
the  mericarps.  (Best  seen  in  specimens  of  fennel 
that  have  lain  in  water  an  hour  or  two.)1 

II.  Compare  the  three   fruits  more  in  detail,  using  a 
good  lens  for  the  purpose.     Observe 

1.  The  number  and  position  of  the  ribs.     Begin  with 

fennel,  in  which  it  is  at  once  seen  that  each  meri- 
carp has  five  strong  ribs,  two  lateral,  one  dorsal, 
arid  two  intermediate.  How  does  the  dill  fruit 
compare  in  this  respect  ? 

The  coriander  fruit  differs  remarkably  from  either  of 
the  preceding.  If  a  mericarp  is  carefully  studied, 
it  will  be  seen  to  have  five  primary  ribs,  corre- 
sponding to  those  of  fennel,  but  wavy  in  outline 
and  less  prominent  than  four  secondary  ribs  alter- 
nating with  them. 

2.  Remains  of  floral  envelopes.     If  uninjured  specimens 

are  examined,  it  will  be  seen  that  the  calyx  teeth  of 
the  coriander  are  conspicuously  present  at  the  apex 
of  the  fruit.  Is  this  true  of  the  dill  and  fennel  ? 

III.  Prepare  transverse  sections  of  the  mericarps  of  all 
three  species,  and  examine  with  the  low  power  of  a  com- 
pound microscope.     In  each  case  it  will  be  necessary  to 
take  at  least  two  sections,  one  near  the  apex  of  the  fruit, 
and  one  near  the  middle  or  lower  down. 


206  STUDY   OF   COMMON   PLANTS. 

It  will  be  seen  that  all  three  kinds  have  a  relatively 
thick  pericarp  and  abundant,  white  endosperm,  within  which 
lies  the  small  embryo,  near  the  apex  of  the  fruit,  and  con- 
sequently not  seen  in  sections  taken  lower  down.  In  the 
pericarp  are  a  number  of  vittae,  or  oil-tubes.  The  corian- 
der has  two  of  these  in  each  mericarp  lying  next  to  its  in- 
ner, or  ventral  face.  In  fennel  and  dill,  in  addition  to 
these  two,  there  are  four  more  vittse  alternating  with  the 
ribs  of  the  outer,  or  dorsal  face. 

Draw  in  outline,  representing  accurately  the  position  of 
ribs  and  vittse.  Letters  and  guiding  lines  will  conduce  to 
clearness. 

IV.  Write  a  complete  description  of  the  three  fruits, 
taking  care  to  distinguish  the  characters  common  to  all, 
from  those  that  are  only  of  specific  or  generic  value. 

RELATIONSHIP. 

Later  in  the  season  many  other  species  of  umbellifers 
that  will  serve  for  comparative  study  are  easily  obtained. 
Thaspium,  or  some  other  common  genus,  may  be  substi- 
tuted for  Erigenia  if  found  more  convenient.  As  the 
study  is  continued  it  will  be  apparent  that  the  external 
characters  to  which  attention  has  already  been  directed, 
although  variously  modified,  are  constantly  repeated  in 
nearly  all  the  genera.  The  hollow  stem,  compound  leaves 
with  inflated  petioles,  flowers  in  umbels,  and  the  very 
marked  and  distinctive  features  of  flowers  and  fruit  occur 
over  and  over  again,  sometimes  in  connection  with  specific 
characters  by  which  a  given  plant  is  easily  identified,  some- 
times with  these  characters  so  far  wanting  that  identifica- 
tion becomes  extremely  difficult.  All  in  all,  the  family  is 
one  of  the  best  marked  groups  in  the  vegetable  kingdom. 
It  includes  about  thirteen  hundred  species,  distributed 


THE   PARSLEY   FAMILY.  207 

chiefly  over  the  temperate  regions  of  the  globe.  They  are 
remarkable  for  their  widely  different  active  properties,  a 
considerable  number  being  edible,  a  large  proportion  pleas- 
antly (or  unpleasantly)  aromatic,  and  a  comparatively  small 
number  poisonous.  It  is  a  curious  fact  that  while  very 
largely  dependent  upon  insects  for  fertilization,  the  flowers 
of  umbellifers  attract,  as  a  rule,  a  very  common  lot  of  visit- 
ors such  as  "  short-lipped  flies,  beetles,  and  other  short- 
lipped  insects  in  immense  variety." l  Numbers,  rather 
than  quality,  has  become  the  rule,  and  while  the  family 
has  held  its  own,  and  has  even  established  a  claim  to  be 
considered  one  of  the  dominant  natural  orders,  it  is  one 
of  the  least  attractive. 

The  best  preparation  for  the  further  study  of  this  rather 
difficult  family  will  be  made  by  getting  together  a  collec- 
tion of  ripe  fruits,  especially  those  occurring  in  commerce, 
and  becoming  thoroughly  familiar  with  their  anatomical 
structure. 

Useful  directions  for  collecting  and  other  needed  sug- 
gestions are  given  by  Coulter  and  Rose,  in  their  Revision 
of  North  American  Umbelliferce? 

SPECIAL   STUDIES. 

I.    Morphology  of  the  "tuber"  of  Erigenia  bulbosa. 

A  critical  botanist  writes  :  "  Is  it  really  a  stem  ? 
Who  ever  examined  it?     It  appears  to  me  to  be 
half  hypocotyl,  and  the  other  half  a  root." 
II.    The  terminal,  colored  flower  of  Daucus  Carota. 

1  Mtiller,  Fertilization  of  Flowers,  p.  287. 

2  Separate  monograph.     Issued  by  the  Herbarium  of  Wabash  College, 
December,  1888. 


208  STUDY    OF   COMMON    PLANTS. 


XXXIII.    THE   MILKWEED    FAMILY. 
ASCLEPIADACE^E. 

MATERIAL   REQUIRED. 

Flowers  of  Asclepias  Cornuti,  Decaisne.  Alcoholic  specimens  will 
serve  if  fresh  ones  are  not  to  be  had,  but  there  is  an  advantage 
in  having  a  supply  of  both. 

MILKWEED.     Asclepias  Cornuti,  Decaisne. 
Flowers. 

Our  study  of  the  milkweed  will  be  restricted  to  the 
flowers,  which  present  an  extraordinary  mechanism  for 
securing  cross-fertilization  through  the  agency  of  insects. 
They  are  borne  in  a  conspicuous  umbel  and  attract  numer- 
ous visitors,  particularly  bees,  wasps,  and  flies.  Both  the 
odor  and  color  are  attractive,  and  there  is  an  abundant 
supply  of  nectar.  The  plant  is  absolutely  dependent  on 
insects  for  fertilization. 

Observe  first  the  form  and  position  of  the  floral  envel- 
opes. They  are  reflexed  and  covered  on  their  lower 
surface  with  short,  woolly  hairs.  (This  is  contrary  to 
the  general  rule  noticed  by  Kerner,  Flowers  and  their  Un- 
bidden G-uests,  that  plants  protected  by  milky  juice  have 
smooth  leaves,  and  are  without  any  other  appliances  for 
the  protection  of  their  flowers  from  crawling  animals.) 

The  crown  is  the  most  conspicuous  part  of  the  flower. 
It  consists  of  five  hollow  bodies,  cuculli,  each  of  which  has 
an  incurved  horn  projecting  from  its  opening. 


THE    MILKWEED    FAMILY.  209 

There  are  five  anthers  placed  close  together,  each  ter- 
minating in  a  membranous  appendage  that  projects  over 
the  thickened  stigma  disk. 

The  anthers  are  separated  from  each  other  laterally  by 
a  deep,  vertical  slit,  bordered  on  either  side  by  a  thin 
triangular  process,  the  anther  wing.  At  the  upper  ex- 
tremity of  the  slit  is  a  minute,  black  body,  corpusculum, 
which,  when  removed  by  a  needle,  is  found  to  be  con- 
nected by  means  of  a  delicate,  curved  band  on  either  side, 
with  a  flattened,  yellow,  and  waxy  pollen-mass,  pollinium. 
Longitudinal  swellings  on  the  outside  of  each  anther  indi- 
cate the  position  of  the  pollinia  before  their  removal. 

Each  of  the  slits  already  described  is  continuous  within 
with  the  stigmatic  chamber,  into  which  the  pollen  must  be 
introduced  in  order  that  fertilization  may  take  place.  It 
is  obvious  that  this  cannot  happen  unless  the  pollinia  are 
removed  from  the  anthers,  and  brought  into  the  stigmatic 
chambers  by  some  external  agency. 

This  is  accomplished  by  bees  and  other  insects  that  visit 
the  flowers  for  honey.1  Alighting  on  the  umbel  the  insect 
easily  gets  its  foot  caught  in  the  lower  part  of  one  of  the 
slits,  and  in  attempting  to  withdraw  it,  one  of  the  claws 
is  guided  into  the  notch  in  the  lower  end  of  the  corpus- 
culum. With  a  strong  pull,  the  latter  is  removed  from  its 
place,  and  the  insect  carries  away  with  it  the  two  pollinia, 
which  by  the  twisting  of  the  delicate  bands,  retinacula, 
that  connect  them  with  the  corpusculum,  are  now  brought 
into  such  a  position  as  to  be  readily  introduced  into 
the  slit  leading  to  the  stigmatic  chamber  of  some  other 
flower.  If  this  has  been  done,  and  the  insect  is  strong 
enough,  it  frees  itself  by  a  vigorous  pull,  breaking  the 

1  Ilildebrand  and  Mtiller  have  given  a  full  account  of  the  process,  the 
latter  writer  with  illustrations.  Fertilization  of  Flowers,  p.  396  et  seq. 


210  STUDY    OF   COMMON    PLANTS. 

retinacula,  and  leaving  the  pollen  masses  in  the  stigmatic 
chamber,  while  it  proceeds  to  other  flowers  and  continues 
gathering  honey. 

Weaker   insects   are   frequently   unable    to    break   the 
retinacula.     Flies  may  often  be  seen  making  unavailing 
efforts   to    extricate    themselves,  and  honey-bees  are  not 
infrequently  found  that   have   been  caught  in  the  same., 
way,  and  have  died  after  prolonged  struggles  to  get  free. 

By  means  of  the  preceding  description,  accompanied  by 
careful  observation  at  each  step,  the  student  will  be  in  a 
position  to  study  the  entire  mechanism  to  advantage.  He 
should  now  go  over  the  whole  independently,  until  every 
part  of  the  flower  is  perfectly  familiar.  The  study  of 
external  structure  should  be  followed  by  a  comparison 
of  cross  and  longitudinal  sections  (best  made  from  alco- 
holic material),  with  sketches  to  show  the  parts  and  their 
relations  to  each  other. 

Several  hours  will  be  required  to  do  this  properly. 
Miiller's  drawings  may  be  consulted,  but  they  are  less 
easily  understood  than  the  flower  itself.  Nothing  can 
possibly  take  the  place  of  direct,  personal,  and  long-con- 
tinued study  of  the  object  under  investigation.  Further, 
it  is  very  desirable  that  the  pupil  should  not  only  under- 
stand the  mechanism,  but  that  he  should  also  see  it  in 
operation.  A  few  days  in  summer  spent  in  watching  the 
flowers  of  the  milkweed,  as  the  visitors  come  and  go,  will 
give  full  opportunity  for  this. 


RELATIONSHIP. 

The  Asclepiadacese  constitute  a  large  and  very  remark- 
able family  of  plants,  including  about  thirteen  hundred 
species,  which  are  largely  tropical,  although  many  repre- 


THE  MILKWEED   FAMILY.  211 

sentatives  occur  in  the  temperate  regions  of  both  hemi- 
spheres. They  are  chiefly  interesting  for  the  extraordinary 
structural  modifications  of  their  flowers,  which  "  rival  the 
orchids,  if  not  in  the  variety  of  their  forms,  at  least  in 
their  complexity  and  their  perfect  adaptation  to  insect 
visitors."  A  study  of  the  steps  by  which  this  gradually 
increasing  complexity  of  structure  has  been  attained  is 
of  the  highest  interest.  The  student  should  carefully  com- 
pare the  flowers  of  other  genera  of  Asclepiadacese,  and 
such  representatives  of  related  families  as  Apocynum, 
Vinca,  and  others. 

SPECIAL   STUDIES. 

I.    It  is  found  that  only  a  very  small  proportion  of  the 
flowers  in  an  umbel  set  fruits.     Why  is  this  ?  and 
are  those  flowers  which  do  not  set  fruits  of  any 
value  to  the  plant  ? 
II.    Minute  structure  of  pollinia  and  retinacula. 

III.  Morphology  of  the  cuculli. 

IV.  Development  of  the  flower. 

V.   Protective  appliances  in  this  family. 


212  STUDY    OF    COMMON   PLANTS. 


XXXIV.    THE   BORAGE   FAMILY. 
BORRAGINACEJE. 

* 
MATERIAL   REQUIRED. 

Common  hound's-tongue,  Cynoglossum  officinale,  L.,  in  flower. 

Similar  specimens  of  any  of  the  following  genera :  Echinospermurn, 
Mertensia,  Lithospermum,  Symphytum,  Heliotropium,  Myosotis. 
Cultivated  species  of  some  of  these,  as  forget-me-not  and  helio- 
trope, will  serve  a  good  purpose. 

HOUND'S-TONGUE.     Cynoglossum  officinale,  L. 
Distribution  and  General  Characters. 

I.  This  species  is  described  as  an  introduced  weed.     Do 
its  habits  confirm  this  statement? 

II.  Examine  the  plant  with  reference  to  general  feat- 
ures.     Note    its   coarse   aspect,    hairy   surface,    and    dis- 
agreeable odor. 

Inflorescence. 

The  inflorescence  is  characteristic  and  should  be  criti- 
cally studied,  as  it  is  of  a  form  that  appears  in  many  rep- 
resentatives of  this  family. 

I.  Notice  first  the  order  of  development  of  the  flowers. 
The  lowest  have  already  formed  their  fruits ;   higher  up 
are  the  open  flowers,  and  at  the  apex  are  the  unopened 
flower  buds. 

II.  The  inflorescence  is  apparently  a  one-sided  raceme. 
Is  it  really  so  ?     Notice  the  position  of  an  open  flower.     Is 
it  terminal  or  lateral  ? 


THE    BORAGE    FAMILY.  213 

III.  Compare  a  number  of  inflorescences  with  reference 
to  the  occurrence  of  bracts.     Read  Gray,  Structural  Botany, 
pp.  153-155. 

IV.  If  they  can  be  obtained  at  the  same  time,  compare 
the  inflorescence  of  other  representatives  of  the  Borragi- 
naceae,  such  as  puccoon  and  forget-me-not,  with  that  of 
fyound's-tongue.     Do  they  agree  essentially  in  the  arrange- 
ment of  flowers  ? 

Flower. 

I.  Note  first  the  numerical  plan  of  the  flower.     Is  the 
number  five  maintained  throughout  ? 

II.  Observe  the  peculiar  structure  of  the  corolla,  par- 
ticularly the  conspicuous  folds  or  scales  arching  over  the 
essential  organs.     Is  the  flower  perfectly  regular  ? 

III.  Taking  a  recently  opened  flower,   make  a  longi- 
tudinal section  so  as  to  show  the  precise  relation  of  all  the 
parts.     Draw. 

Does  the  position  of  stigma  and  anthers,  and  the  mode 
of  dehiscence  of  the  latter,  afford  any  indication  as  to  the 
way  in  which  pollination  is  effected? 

IV.  Examine  the  ovary,  noting  the  number  of  its  divis- 
ions, and  their  form  and  position. 

Fruit. 

I.  Study  the  fruit  in  different  stages  of  development, 
taking  flowers  of  different  ages  for  the  purpose.  Observe 

1.  Its  rapid  increase  in  size. 

2.  The  formation  of  peculiar  barbed  appendages,  thickly 

covering  its  surface. 

II.  Make  longitudinal  sections  of  young  fruits  so  as  to 
show  the  form  and  position  of  the  seed.  Compare  with 
similar  sections  of  older  fruits. 


214  STUDY    OF   COMMON    PLANTS. 

RELATIONSHIP. 

Compare  with  this  species  as  many  others  of  the  same 
family  as  can  be  obtained.  Note  especially 

I.  Any  general  external  characters  in  which  they  agree. 

II.  The  inflorescence,  which  in  this  family  presents  very 
interesting  peculiarities. 

III.  The  structure  of  'the  flowers,  differing  in  details  in 
the  different  genera,  but  showing  marked  agreement  in 
plan. 

IV.  The  characteristic  fruit. 

V.  Structure  and  position  of  the  seeds. 

Write  a  brief  summary  of  the  features  that  you  consider 
characteristic  of  the  family. 

The  Borraginaceee  include  about  twelve  hundred  species, 
widely  distributed  throughout  the  world.  A  number  of 
ornamental  ones  are  common  in  cultivation.  Some  have 
been  employed  in  medicine,  and  the  curious  doctrine  of 
signatures  is  still  called  to  mind  by  such  names  as  lung- 
wort and  stone  wort.  The  marked  variety  of  external 
appearance,  in  connection  with  great  persistence  of  essen- 
tial characters,  as  seen,  for  example,  by  comparison  of  the 
exquisitely  beautiful  and  fragrant  heliotrope  with  the 
coarse  and  rank  hound's-tongue,  is  interesting  as  suggest- 
ing how  widely  the  different  genera  have  diverged  in 
externals  from  earlier  forms,  while  still  retaining  their 
most  deeply  seated  ancestral  traits. 

The  student  will  do  well  to  make  a  special  study  of  the 
inflorescence  as  it  presents  itself  in  various  members  of 
the  family,  and  in  the  same  connection  review  the  whole 
subject  of  floral  arrangement  as  presented  by  Gray,  Les- 
sons, Sec.  VIII,  or  Structural  Botany,  Chap.  V. 


THE  MINT  FAMILY.  215 


XXXV.   THE   MINT   FAMILY.     LABIATJE. 

MATERIAL   REQUIRED. 

Specimens  of  ground-ivy,  Nepeta  Glechoma,  Benth.,  in  flower. 
Similar  specimens  belonging  to  different  genera  of  the  Mint  family, 
as  they  can  be  obtained.     See  list  below. 

GROUND-IVY.     Nepeta  Glechoma,  Benth. 
Distribution. 

As  in  previous  studies,  notice  the  habitat  and  consider 
the  evidence  as  to  whether  this  is  an  introduced  or  indige- 
nous species.  Gray,  in  the  Manual,  says  "naturalized 
from  Europe."  What  is  meant  by  this? 

General  Characters. 

I.  Observe  first  the  most  obvious  characters,  among 
them  the  following: 

1.  The  habit  of  the  plant,  its  stem  creeping  and  taking 

root  at  short  intervals.     Describe  the  root  system. 

2.  The  characteristic  odor. 

3.  The    shape    of   the   stem   and   arrangement   of    the 

leaves. 

NOTE. —The  aromatic  properties,  square  stem,  and  opposite 
leaves  are  characteristic  not  only  of  this  species  but  of  the  whole 
family  to  which  it  belongs. 

4.  The  relation  of  leaves  and  stem.     Note  particularly 

the    ridges  connecting  the  bases  of   each   pair  of 
petioles,    and    their    chevaux-de-frise    of    bristly 


216  STUDY    OF   COMMON   PLANTS. 

hairs.     Which  way  are  the  latter  directed  ?    What 
do  you  infer  as  to  their  use  ? 

5.  Structural  features  of  the  leaves.  Describe  their 
form  and  venation.  With  a  good  lens  examine 
closely  the  surface  and  margin.  Are  they  smooth 
or  rough  ? 

II.  Study  the  plant  throughout  with  reference  to  its 
various  means  of  protection  and  their  efficiency. 

Inflorescence. 

I.  The   flowers   are    in   small   axillary  clusters.     How 
many  in  each  group?     In  what  order  do  they  open?     Is 
this  order  constant?     Classify  the  inflorescence,  giving  its 
appropriate  name.1 

II.  Are  there  any  arrangements,  in  addition  to  those 
already  noticed,  for  the  protection  of  the  flower? 

Flower. 

I.  Study  critically  the  plan  of  the  flower.     How  many 
calyx-teeth  are  there  ?     How  many  lobes  of  the  corolla  ? 

Remove  the  corolla  with  a  pair  of  fine  forceps,  and  lay 
it  open  by  making  a  longitudinal  slit  its  entire  length, 
passing  through  the  middle  of  the  lower  lip.  Fasten  it 
on  a  flat  piece  of  cork  with  needles,  so  as  to  fully  expose 
the  stamens,  and  examine  under  a  dissecting  microscope. 
One  of  the  stamens  has  been  suppressed.  Which  ?  Notice 
the  insertion  of  the  style,  the  peculiar  form  of  the  ovary, 
and  the  nectary  surrounding  its  base. 

II.  Taking  flowers  of  different  ages,  observe  the  fruit 
in  its  various  stages  of  development.     How  many  carpels 
are  there  ?  2 

1  Cf.  Gray,  Structural  Botany,  p.  151. 

2  Cf.  Gray,  Structural  Botany,  p.  296  ;  Luerssen,  Botanik,  p.  1014. 


THE  MINT   FAMILY.  217 

III.  Construct  a  diagram  of  the  flower.    Consult  Eichler, 
Bluthendiagramme,  for  diagrams  and  theoretical  discussion 
of  the  morphology  of  the  flower  of  the  Labiatse. 

IV.  Examine  the  flower  with  reference  to  the  way  in 
which  fertilization  is  accomplished. 

1.  Notice  the  spots  and  lines  on  the  lower  lip  of  the 

corolla.  Examine  different  specimens  and  ascer- 
tain whether  they  are  constant  in  position.  Are 
they  placed  so  as  to  serve  as  path-pointers  ? 

2.  Using  a  needle  or  bristle,  imitate  the  action  of  an 

insect  inserting  its  proboscis  so  as  to  extract  the 
nectar.  Would  it  be  likely  to  come  in  contact 
with  anthers  or  stigma,  or  both  ? 

3.  If  practicable,  examine  flowers,  from  different  locali- 

ties, and  compare  them  as  to  size,  position  of  the 
anthers,  and  other  features.1 

4.  Nepeta  is  reckoned  by  Miiller  among  the  genera  in 

which,  for  at  least  some  of  the  species,  self-fertili- 
zation has  become  impossible.  Does  this  appear 
to  be  the  case  with  Nepeta  Grlechoma  ? 

V.  Compare,  if  they  can  be  obtained,  the  highly  modi- 
fied flowers  of  Sal  via,  either  those  of  the  common  sage,  or 
of  species  cultivated  in  conservatories.2 

RELATIONSHIP. 

Examine  as  many  of  the  following  species  as  practicable, 
comparing  them  with  ground-ivy,  and  noting  all  common 
characters. 

Catnip,  Nepeta  Cataria,  L. 

1  Cf.  Botanical  Gazette,  I,  p.  41,  II,  p.  118  ;  Miiller,  Fertilization  of 
Flowers,  p.  484. 

2  Cf.  Sachs,  Physiology  of  Plants,  p.  794  ;  Muller,  I.e.,  p.  477  etseq. 


218  STUDY    OF    COMMON    PLANTS. 

Wood-sage,  Teucrium  Canadense,  L. 
Richweed,  Collinsonia  Canadensis,  L. 
Spearmint,  Mentha  viridis,  L. 
Wild  mint,  Mentha  Canadensis,  L. 
Wild  bergamot,  Monarda  fistulosa,  L. 
Skullcap,  Scutellaria  galericulata,  L. 
Motherwort,  Leonurus  Cardiaca,  L. 
Dead-nettle,  Lamium  maculatum,  L. 
Cultivated  species  of  Salvia. 

Notwithstanding  the  fact  that  the  Labiatse  include  some 
twenty-six  hundred  species  scattered  over  the  entire  globe, 
they  constitute  a  very  natural  group  of  plants  ;  that  is,  cer- 
tain strongly  marked  characters  are  so  uniformly  present 
that  it  would  almost  seem,  as  some  botanical  writers  have 
suggested,  that  all  the  species  might  be  placed  in  one  great 
genus.  Accordingly  the  distinction  of  genera  in  this 
family  becomes  a  difficult  task.  The  modifications  of  the 
floral  structures  in  those  species  that  have  become  most 
dependent  on  the  agency  of  insects  for  fertilization  are 
peculiarly  interesting.  The  student  may  profitably  devote 
considerable  time  to  the  comparison  of  the  various  species 
of  Salvia,  for  example,  with  each  other  and  with  simpler 
forms.  Another  interesting  subject  of  investigation,  and 
one  throwing  additional  light  on  the  relationship  of  groups 
that  apparently  have  but  little  in  common,  is  the  develop- 
mental history  of  the  fruit,  which  is  essentially  the  same 
in  this  family  as  in  the  Boraginacese. 


THE   NIGHTSHADE  FAMILY.  219 


XXXVI.   THE   NIGHTSHADE   FAMILY. 
SOLANACE^E. 

MATERIAL   REQUIRED. 

The  cultivated  potato  in  flower.     The  tomato  may  be  substituted. 

Specimens  of  matrimony-vine,  Lycium  vulgare,  Dunal,  in  flower,  and 
similar  specimens  of  ground-cherry,  Physalis  pubescens,  L.,  bitter- 
sweet, Solarium  Dulcamara,  L.,  or  other  easily  procurable  repre- 
sentatives of  the  family. 

POTATO.     Solanum  tuberosum, 
Distribution  and  General  Characters. 

The  common  potato  is  indigenous  to  a  portion  of  the 
coast  region  of  western  South  America.  It  has  been 
widely  cultivated  in  the  northern  hemisphere  for  more 
than  three  hundred  years,  apparently  with  little  specific 
change,  there  having  been  no  inducement  to  artificial 
selection  of  any  other  part  than  the  tuber,  which,  however, 
presents  many,  often  striking,  varieties.1 

In  examining  the  cultivated  plant,  study  its  habit,  not- 
ing the  peculiarities  of  stem  and  leaves,  and  the  character- 
istic odor. 

Inflorescence. 

Examine  a  number  of  specimens.  Do  they  agree  in  the 
character  of  the  inflorescence?  Describe  this  and  draw  a 
diagram  showing  the  position  of  the  flowers  and  their 
order  of  development. 

1  Cf.  De  Candolle,  Origin  of  Cultivated  Plants,  p.  45  et  seq. 


220  STUDY   OF   COMMON   PLANTS. 

See  if  you  can  find  a  description  of  this  kind  of  inflores- 
cence in  any  of  the  books  of  reference.  Does  it  correspond 
with  that  of  any  other  family  that  you  have  studied  ? 

Flower. 

I.  Study  the  parts  of  the  flower  in  order  and  describe 
them.  Note  particularly 

1.  The  plan  of  the  flower  and  whether  it  is  strictly 

regular  or  not. 

2.  The  extent  to  which  coalescence  has  taken  place.1 

3.  Whether  there  is  adnation  of  any  parts. 

4.  Form  of  calyx  and  corolla. 

5.  Structure,  position,  and  insertion  of  the  stamens,  and 

their  mode  of  dehiscence. 

6.  Number  of  carpels  composing  the  ovary.     State  the 

evidence  on  which  you  have  determined  this. 

II.  Construct  a  diagram. 

III.  Determine   whether   there    are    any   arrangements 
favoring  cross-fertilization,  and  whether  self-fertilization 
is  possible.2 

Note  the  persistence,  for  at  least  several  hundred  years, 
of  structures  that  under  present  circumstances  are  of  little, 
if  any,  use  to  the  plant,  but  which  if  it  were  neglected  by 
man  and  allowed  to  run  wild,  might  again  be  needed. 

RELATIONSHIP. 

I.  With  the  potato  compare  other  species  of  the  same 
genus,  as  far  as  these  are  procurable,  also  representatives  of 
other  genera  as  Lycopersicum,  Physalis,  Nicandra,  Lycium, 

1  Cf.  Gray,  Structural  Botany,  p.  179. 

2  Cf.  Miiller,  Fertilization  of  Flowers,  p.  425. 


THE   NIGHTSHADE  FAMILY.  221 

and  Petunia.  The  last  two  are  widely  cultivated,  and 
their  flowers  may  be  had  for  weeks  together.  Attention 
should  be  directed  to 

1.  Such  general  external  features  as  the  plants  possess 

in  common.  Between  certain  species  and  genera 
this  likeness  in  general  characters  is  very  striking, 
in  other  cases  it  is  not  apparent. 

2.  Active  properties,  manifested  in  part  by  odor  and 

taste. 

3.  Structure  of  flower  and  fruit. 

4.  Structure  of  seeds.     The  seeds  of  different  plants  of 

this  family  exhibit  great  likeness  of  form  and 
structure,  as  may  be  seen  by  comparing  longitu- 
dinal sections  of  those  of  tomato,  egg-plant, 
stramonium,  etc.  It  is  very  desirable  that  the 
student  should  make  an  extended  and  critical 
comparison  of  the  seeds  of  as  many  different 
species  as  possible.  This  should  be  assigned  as 
a  special  study,  and  time  given  for  a  thorough 
piece  of  work. 

II.  Write  a  summary  of  the  characters  in  which  all  the 
species  examined  agree. 

III.  Compare  the  characters  of  the  Solanaceee  with  those 
of  any  other  families  that  you  remember  as  showing  resem- 
blances to  them.     If  you  have  already  studied  any  of  the 
Scrophulariacese  point  out  the   best  characters  by  which 
the  two  families  are  to  be  distinguished. 

In  the  study  of  every  family,  comparisons  of  this  kind 
should  be  made  as  fast  as  the  necessary  data  are  in  hand. 
In  most  cases  the  relationships  of  families  among  them- 
selves are  by  no  means  as  satisfactorily  made  out  as  could 
be  desired,  but  that  is  no  reason  for  not  studying  them. 


222  STUDY    OF   COMMON    PLANTS. 

The  Solanacese  include  over  twelve  hundred  species, 
chiefly  tropical  and  sub-tropical,  some  representatives, 
however,  being  widely  cultivated  in  temperate  regions. 
Many  of  them  possess  strongly  narcotic  and  poisonous 
properties,  as  the  names  deadly  nightshade,  henbane,  etc., 
indicate.  A  few  are  much  employed  in  medicine.  The 
potato  is  the  most  useful,  the  tobacco  plant  the  most 
harmful  member  of  the  family.  Morphologically  this 
group  of  plants  is  of  interest  in  its  affinities,  more  or  less 
distinctly  marked,  with  several  conspicuous  families,  the 
Scrophulariacese  and  Convolvulacese  among  them.  Physi- 
ologically it  offers  comparatively  little  of  special  impor- 
tance, although  some  species  exhibit  interesting  adaptations 
for  insuring  fertilization. 


THE  FIGWORT  FAMILY.  223 


XXXVII.    THE   FIGWORT   FAMILY. 
SCKOPHULAKIACE^. 

MATERIAL   REQUIRED. 

Butter-and-eggs,  Linaria  vulgaris,  Mill.,  in  flower. 
Common  species  of  any  of  the  genera  named  below. 

BUTTER-AND-EGGS.     Linaria  vulgaris,  Mill. 
Distribution. 

In  what  situations  have  you  seen  the  plant  growing? 
Have  you  made  any  observations  as  to  its  natural  range  ? 
Is  there  anything  in  its  habits  that  affords  evidence  as  to 
whether  it  is  indigenous  or  introduced  ? 

General  Characters. 

I.  This  species  is  perennial.     How  is  the  fact  ascer- 
tained ? 

II.  Describe    the    underground   portion   of    the    plant. 
The  stem  and  leaves. 

III.  Is  there  anything  about  it  that  secures  protection 
from  grazing  animals  ? 

Inflorescence. 

Character  and  kind  of  inflorescence.  Notice  the  posi- 
tion of  the  individual  flowers.  Do  they  all  face  outward  ? 
Do  the  position  of  the  flowers  and  the  order  of  their 
development  present  any  advantages  ? 


224  STUDY   OF    COMMON    PLANTS. 

Flower. 

I.  Study  the  plan  of  the  flower.     What  is  the  original 
numerical  plan  as  indicated  by  the  floral  envelopes?     Is 
this  plan  apparent  in  the  androecium  ?     In  the  gynsecium  ? 
How  many  perfectly  developed  stamens  are  there?     See 
if  you  can  find  traces  of  another  one.     If  so,  how  does  it 
compare  with  the  rest?     How  many  carpels  compose  the 
pistil?     On  what  evidence  is  this  determined? 

II.  Construct  a  diagram  of  the  flower.     If  you  find  a 
trace  of  a  fifth  stamen,  mark  its  place  with  an  x. 

III.  Examine   a  transverse   section  of   an   ovary  from 
which  the  corolla  has  fallen,  and  notice  the  arrangement 
of  the  ovules,  and  the  position  and  form  of  the  placentae. 
In  a  still  older  ovary  observe  the  form  and  structure  of 
a  young  seed. 

IV.  When  the  capsules  are  ripe  study  their  structure 
and  mode  of  dehiscence. 

V.  Study  carefully  the  adaptations  for  securing  fertili- 
zation by  the  agency  of  insects.     Begin  with  the  corolla 
and  note 

1.  Its  bilabiate  form. 

2.  The  conspicuous  palate  and  its  color  as  compared 

with  the  rest  of  the  corolla. 

3.  The  spur.     Where  is  the  nectar?     Is  it  easily  acces- 

sible to  all  sorts  of  visitors?  Imitate  the  action 
of  a  bee  in  gathering  honey.  Depress  the  lower 
lip  by  pushing  down  the  palate  with  a  needle. 
Are  there  any  path-pointers  ?  Notice  the  position 
of  anthers  and  stigma. 

If  possible,  watch  a  bee  visiting  a  plant,  and  observe 
the  mutual  relations  of  insect  and  flower. 


THE   FIGWORT    FAMILY.  225 

This  plant  has  been  widely  introduced  into  the  United 
States,  and,  notwithstanding  its  botanical  interest,  is  a 
pernicious  weed,  difficult  to  eradicate.  Aside  from  repro- 
duction by  seed,  it  persistently  maintains  itself  by  means 
of  its  rhizomes,  each  of  which  sends  up  several  or  many 
aerial  shoots.  The  unpleasant  odor  and  taste  of  the 
plant  render  it  distasteful  to  grazing  animals,  so  that 
it  is  efficiently  protected  by  its  own  disagreeable  prop- 
erties. 

The  adaptations  for  securing  cross-fertilization  by  the 
agency  of  insects  are  striking,  and,  for  the  most  part, 
easily  understood.  The  flowers  are  rendered  conspicuous 
by  massing  in  a  crowded  raceme,  and  face  outward,  so  a3 
to  be  immediately  accessible  to  flying  insects,  while  the 
orange-colored  palate,  with  its  smooth  median  groove  on 
the  inner  side,  directs  visitors  at  once  to  the  nectar  col- 
lected in  the  spur.  The  anthers  and  stigma  are  so  dis- 
posed as  to  come  in  contact  with  the  head  and  back  of 
the  insect  (commonly  a  bee),  as  it  depresses  the  palate 
and  inserts  its  long  proboscis  into  the  spur.  While  thus 
accessible  to  large  insects  with  a  long  proboscis,  the  nectar 
is  protected  from  unbidden  guests  by  the  palate,  that  com- 
pletely closes  the  throat  of  the  flower,  and  springs  back 
to  its  place  when  the  force  by  which  it  is  depressed  ceases 
to  act.  It  is  further  protected  by  its  position,  being  out 
of  the  reach  of  insects  with  a  short  proboscis  that  may 
in  some  way  have  effected  an  entrance  into  the  flower. 

The  mechanical  arrangements  for  the  dissemination  of 
the  seeds  are  also  of  interest.  The  hygroscopic  action  of 
the  capsules  is  readily  shown  by  placing  them  when  dry 
in  water.  In  less  than  a  minute  the  teeth  at  the  apex 
begin  to  bend  inwards,  and  in  a  short  time  the  capsule  is 
tightly  closed,  opening  again  when  it  has  been  thoroughly 


226  STUDY    OF   COMMON    PLANTS. 

dried.  In  this  way  the  seeds  are  scattered  when  the 
weather  is  most  favorable  for  their  being  conveyed  to 
some  distance.  On  the  whole,  the  plant  with  its  simple 
but  effective  means  of  protection,  persistent  subterranean 
stems,  admirable  adaptations  for  cross-fertilization,  and 
numerous  seeds  with  special  arrangements  for  dissemi- 
nation, is  exceedingly  well  adapted  to  survive  in  the 
struggle  for  existence. 

RELATIONSHIP. 

I.  Compare  several  of  the  following  plants  with  the 
species  just  studied,  directing  attention  particularly, 
though  not  exclusively,  to  the  flowers.  (Some  of  these 
that  bloom  earlier  than  the  Linaria,  as  the  wood-betony, 
may  be  studied  before  the  latter  if  more  convenient.) 

Wood-betony,  Pedicularis  Canadensis,  L. 
Painted-cup,  Castilleia  coccinea,  Spreng. 
Beard-tongue,  Pentstemon  pubescens,  Solander. 
Turtle-head,  Chelone  glabra,  L. 
Monkey-flower,  Mimulus  ring  ens,  L. 
Various  species  of  Veronica. 

Some  cultivated  species  also  may  be  used  such  as 
"  Kenil worth  ivy,"  Linaria  Cymbalaria,  Mill. 
Snapdragon,  Antirrhinum  majus,  L. 
Foxglove,  Digitalis  purpurea,  L. 

How  do  these  compare  as  regards 

1.  Plan  of  the  flower? 

2.  Shape  of  corolla  ? 

3.  Number  of  stamens  ? 

4.  Structure  of  ovary  ? 

5.  Number  and  position  of  seeds  ? 


THE   FIGWORT   FAMILY.  227 

II.  State  concisely,  and  in  general  terms,  what  charac- 
ters you  have  found  to  be  common  to  all  the  species 
studied. 

There  is  evidence  that  the  Scrophulariacese  are  an  old 
family  of  plants,  and  one  that  may  fairly  be  reckoned  to 
have  gained  a  place  among  the  dominant  groups.  There 
are  nearly  two  thousand  species  distributed  over  the  entire 
globe.  While  well  marked  as  regards  family  characters, 
the  different  genera  and  species  exhibit  very  wide  diver- 
gence of  structure,  often  associated  with  peculiarities  of 
color  that  stand  in  evident  relation  to  the  insects  on  which 
they  have  come  to  depend.  A  considerable  number  have 
entirely  lost  the  capacity  for  self-fertilization,  and  the 
mechanical  arrangements  are  in  some  cases  so  complicated 
as  to  be  difficult  of  explanation.  The  gradation  of  forms 
from  comparatively  simple  ones  to  others  that  show 
remarkable  adaptations  to  highly  specialized  insects,  offers 
a  peculiarly  interesting  study  of  developmental  history.1 

SPECIAL    STUDIES. 

I.    Morphology  of  the  flower  of  the  Scrophulariacese. 
II.    Peloria  in  this  family  and  its  significance. 

III.  Comparison  of  mechanisms  by  which  fertilization  is 

effected  in  different  genera  of  Scrophulariacese. 

IV.  Exclusion    of   unbidden    guests  as  accomplished   in 

Pentstemon  and  other  genera. 

V.    The   genus   Veronica.      A  comparison    of   different 
species  of  the  genus,  and  of  the  genus  itself  with 
other  representatives  of  the  family. 
1  Cf .  Mtiller,  Fertilization  of  Flowers,  pp.  429-465. 


228  STUDY   OF    COMMON    PLANTS. 


XXXVIII.    THE   HONEYSUCKLE   FAMILY. 
CAPRIFOLIACEJE. 

MATERIAL   REQUIRED. 

Common  elder,  Sambucus  Canadensis,  L.,  in  flower.  Other  specimens 
of  the  same  species,  with  the  fruit  partially  developed.  Species 
of  Viburnum,  coming  earlier  in  the  season,  may  be  substituted. 

Any  of  the  indigenous  species  of  Lonicera,  Diervilla,  Symphoricarpus, 
Linnsea,  and  Triosteum  that  are  procurable. 

COMMON  ELDER.     Sambucus  Canadensis,  L. 

Distribution. 

In  what  situations  have  you  observed  the  plant  growing  ? 
Is  it  indigenous  ? 

General  Characters. 

I.  Record  what  you  have    noticed   as   to  its  mode  of 
growth.     Is  its  habit  that  of  a  shrub  or  of  a  tree  ? 

II.  Mode  of  branching.     Differences  observed  in  differ- 
ent specimens. 

III.  Do  the   stems    exhibit  any  peculiarities   of   form, 
structure,  or  surface  markings?     If  so,  describe  in  detail. 

NOTE.  —  The  lenticels  are  generally  a  conspicuous  feature.  For  an  ac- 
count of  these,  see  Strasburger  and  Hillhou.se,  Practical  Botany,  pp.  153, 
154. 

IV.  Describe  the  leaves.     Note  variations. 


THE    HONEYSUCKLE   FAMILY.  229 

Inflorescence. 

I.  Observe    the    number    and    position    of    the    main 
branches.     Compare  specimens  until  the  normal  arrange- 
ment is  clearly  understood. 

II.  Ascertain  the  order  of  development  of  the  flowers. 
Take  a  small  division  of  the  inflorescence,  to  avoid  confu- 
sion, and  represent  it  on  paper  diagrarnmatically.1 

III.  Classify  the  inflorescence.2     Does  such  an  arrange- 
ment of  flowers  present  any  physiological  advantages  ? 

Flower  and  Fruit. 

I.  What  is  the  numerical  plan  of  the  flower  ?     Is  this 
constant  in  all  the  specimens  ?     Is  it  exhibited  in  all  the 
whorls  ? 

II.  Note  the  relation  of  the  different  whorls  to  each 
other.     Is  the  ovary  superior  or  inferior?     Where  are  the 
stamens  attached? 

III.  Does  the  relative  position  of  anthers  and  stigma 
favor  cross-  or  self-fertilization,  or  both  ? 

IV.  Make  transverse  sections  of  a  number  of  immature 
fruits.     Are  they  all  alike  ?     Draw  a  section  that  you  con- 
sider typical.     Compare  the  ripe  fruits,  if  they  are  to  be 
had,  and  note  the  changes  that  have  taken  place.    Describe 
and  classify  the  fruit. 

RELATIONSHIP. 

The  relationship  of  the  common  elder  must  necessarily 
be  made  a  subject  of  special  study  rather  than  a  piece  of 
class  work,  since  the  indigenous  species  of  Caprifoliacese 

1  Cf.  Bessey,  Botany,  pp.  138,  139. 

2  Cf.  Gray,  Structural  Botany,  pp.  151,  152. 


230  STUDY   OF   COMMON   PLANTS. 

flower,  for  the  most  part,  at  widely  different  times,  and 
some  of  the  genera  exhibit  among  themselves  such  marked 
structural  differences  as  to  obscure,  except  to  a  trained 
eye,  the  common  family  characters.  The  contrast  between 
the  simple,  open  flowers  of  the  elder  and  the  extremely 
elongated  corolla  of  species  of  Lonicera  that  have  become 
adapted  to  the  visits  of  night-flying  moths,  is  a  striking 
example.  The  student  who  wishes  to  familiarize  himself 
with  this  family,  which  presents  many  interesting  features, 
will  find  in  the  course  of  spring  and  summer  enough 
indigenous  species  of  the  genera  named  above  to  enable 
him  to  make  a  fairly  extended  comparative  study.  The 
clue  to  the  wide  divergence  of  form,  and  the  remarkable 
series  of  colors  exhibited  by  flowers  of  the  different  genera, 
is  apparently  found  in  progressive  adaptation  to  different 
insect  visitors.1 

Another  remarkable  feature  is  the  great  difference  of 
habit  exhibited  by  different  members  of  the  family,  as 
seen,  for  example,  in  a  comparison  of  the  slender,  trailing 
Linnaea  with  the  coarse,  upright  Triosteum,  or  the  climb- 
ing species  of  Lonicera  with  the  shrubs  or  trees  of  the 
genera  Sambucus  and  Viburnum.  Even  within  the  limits 
of  a  single  genus,  as  in  the  case  of  Lonicera  and  Viburnum., 
wide  differences  of  structure  and  habit  present  themselves, 
affording  an  opportunity  to  observe  adaptations  that  ap- 
pear to  have  been  acquired  within  comparatively  recent 
times. 

1  Cf .  Miiller,  Fertilization  of  Flowers,  p.  299. 


THE  GOURD   FAMILY.  231 


XXXIX.   THE   GOURD   FAMILY. 
CUCURBITACE^E. 

MATERIAL   REQUIRED. 

The  common  cucumber,  Cucumis  sativus,  L.,  in  flower.1 
Similar  specimens  of  squash,  melon,  wild  cucumber  or  gourd. 
Seeds  of  pumpkin,  melon,  arid  various  other  cucurbits. 

CUCUMBER.     Cucumis  sativus,  L. 
Distribution. 

The  cucumber  has  been  widely  cultivated  from  an  early 
date,  and  presents  a  remarkable  case  of  the  persistence  of 
specific  characters  for  an  indefinite  period.  According  to 
De  Candolle,  it  has  been  cultivated  in  India  no  less  than 
three  thousand  years,  yet  its  wild  form  found  at  the  foot 
of  the  Himalayas  has  stems,  leaves,  and  flowers  that  are 
"  exactly  those  of  Cucumis  sativus"  2 

General  Characters. 

I.  Note  first  the  habit  of  the  plant  as  regards  position 
and  direction  of  growth.     Is  it  capable  of  supporting  itself 
in  an  erect  position  ?     How  do  young  specimens  compare 
with  older  ones  in  this  respect  ? 

II.  Observe  the  leaf  arrangement. 

III.  Is  the  plant  protected  in  any  way  ?     Examine  the 

1  Well-formed    plants,  with  flowers  and  young  fruits,  are  easily  ob- 
tained by  sowing  the  seeds  in  flower-pots  a  few  weeks  before  the  speci- 
mens are  wanted. 

2  Origin  of  Cultivated  Plants,  pp.  264-266. 


232  STUDY    OF   COMMON    PLANTS. 

surface  of  stems,  leaves,  flowers,  and  fruit,  first  with  the 
naked  eye,  and  then  with  a  good  lens.  Imagine  a  soft- 
bodied  animal  attempting  to  crawl  up  to  the  leaves  or 
flowers.  Which  parts  are  best  protected  ? 

Tendrils. 

I.  Study  carefully  the  tendrils,  noting  particularly  their 
origin,  form,  and  mode  of  grasping  a  support.     How  do 
they  compare  in  their  subsequent  behavior  with  those  of 
bryony,  described  by  Sachs  ? 1 

II.  Rub  one  of  the  young  tendrils  and  watch  it  for  a 
few  minutes.     Is   there  any  movement?     Does    it   make 
any  difference  whether   the    concave    or   convex    side   is 
rubbed  ?  2 

III.  Watch  a  vigorous  specimen  long  enough  to  observe 
the  spontaneous  movements  of  its  tendrils. 

Inflorescence  and  Flowers. 

I.  How  many  flowers  compose  the  inflorescence?     Are 
they  all  alike  ?     Compare  those  in  the  axils  of  the  lower 
leaves  with  the  ones  produced  higher  up.     Is  this  species 
monoecious  or  dioecious?3 

II.  Examine    carefully  the   stamens,  noting   the    form 
and  structure  of  the  anthers  and  their  peculiar  mode  of 
cohesion.4 

III.  How  many  stigmas  are  there  ?     Examine  their  sur- 
face with  a  lens. 

IV.  Are  there  any  nectaries  ?     How  far  do  the  flowers 
of  the  cucumber  agree  with  those  of  Bryonia  dioica,  as 

1  Physiology  of  Plants,  pp.  663,  664. 

2  Cf.  Darwin,  Climbing  Plants,  p.  127  et  seq. 

3  Cf.  Gray,  Lessons,  p.  85. 

*  Cf.  Goebel,  Outlines  of  Classification  and  Special  Morphology,  p.  357. 


THE   GOURD    FAMILY.  233 

described  by  Mallei'?1     Does  their  structure  indicate  self- 
or  cross-fertilization  ? 

V.  Examine  the  ovary  of  one  of  the  oldest  flowers. 
Is  there  any  external  indication  of  the  number  of  carpels? 

Make  a  transverse  section  and  notice  the  number  of 
cells,  the  position  of  the  placentae,  and  the  form  and  direc- 
tion of  the  ovules.  Draw  the  section  in  outline.  Repre- 
sent by  dotted  lines  the  commissural  lines  of  union  of  the 
carpellary  leaves.2 

RELATIONSHIP. 

Seeds  of  squash,  melon,  and  many  other  plants  belonging 
to  this  family,  are  easily  procurable,  and  afford  the  means 
of  extended  and  instructive  comparative  study.  Seedlings, 
which  may  be  had  in  the  course  of  a  few  days,  exhibit 
with  remarkable  uniformity  in  the  different  genera  the 
characteristic  contrivance  by  which  the  seed-coats  are 
ruptured  and  the  cotyledons  released.3  Tendrils  of  vari- 
ous species,  that  may  be  studied  anywhere  a  little  later 
in  the  season,  are  of  the  greatest  interest,  morphologically 
as  well  as  physiologically,  and  in  their  turn  contribute  to 
the  sum  of  characteristic  features  by  which  this  famil}r  is 
marked.  If  all  these  are  carefully  studied,  as  well  as  the 
flowers  and  fruits,  and  due  weight  is  given  to  every  well- 
marked  trait,  it  will  be  found  that  the  "  family  characters" 
include  more  than  the  structural  details  usually  given. 
The  behavior  of  the  seedlings  in  breaking  through  the 
ground,  the  highly  developed  tendrils  and  their  mode  of 
action,  and  even  the  active  properties  of  some  of  the 

1  Fertilization  of  Flowers,  pp.  268,  269. 

2  Cf.  Eichlor,  Bliithendiagramme,  p.  306. 

3  Darwin,  Power  of  Movement   in  Plants,  p.  102. 


234  STUDY    OF    COMMON    PLANTS. 

species  are  as  truly  characteristic  as  various  other  features 
upon  which  more  emphasis  is  usually  laid. 

The  student  is  recommended  to  make  a  special  study  of 
seeds  and  seedlings  of  the  Cucurbitacese,  and  to  proceed 
from  these,  as  material  and  opportunity  permit,  to  the 
characters  observable  in  later  stages  of  growth. 


THE   COMPOSITE  FAMILY.  235 


XL.    THE   COMPOSITE   FAMILY.    COMPOSITE. 

MATERIAL   REQUIRED. 

Specimens  of  the  common  dandelion  in  flower,  others  with  the  fruits 

in  different  stages  of  development. 
Similar  specimens  of  robin's-plantain,  Erigeron  bellidifolius,  Muhl.  (or 

other  species  of  Erigeron),  plantain-leaved  everlasting,  Antennaria 

plantaginifolia.  Hook.,  golden  ragwort,  Senecio  aureus,  L. 
Later  in  the  season,  yarrow,  A chillea  Millefoiium,  L.,  mayweed,  Anthe- 

mis  Cotula,  DC.,  oxeye  daisy,  Chrysanthemum  Leucanthemum,  L., 

wild  lettuce,  Lactuca  Canadensis,  L, 
In  the  fall,  asters,  goldenrods,  and  various  species  of  Bidens,  Prenan 

thes,  and  other  late  flowering  composites. 

THE   DANDELION.     Taraxacum  officinale,  Weber. 
Distribution. 

Where  were  the  specimens  gathered?  Does  the  plant 
manifest  any  choice  of  locality  or  surroundings?  Is  it  an 
indigenous  or  introduced  species  ? 

General  Characters. 

With  a  perfect  specimen  in  hand,  note  the  several  parts 
of  the  plant  and  write  a  brief  description,  including  an 
account  of  the  form,  structure,  and  apparent  duration  of 
the  root,  the  stem  (so  short  that  the  plant  is  said  to  be 
acaulescent),  the  position  and  form  of  the  leaves,  the 
character  of  the  inflorescence  and  its  support,  and  any 
conspicuous  peculiarities,  such  as  taste,  color  of  the  latex, 
etc. 


236  STUDY   OF   COMMON    PLANTS. 

Inflorescence. 

I.  Observe   first  the   cylindrical   hollow   stalk   (scape) 
by  which  the  head  is  supported.     How  do  those  of  older 
specimens  compare  in  length  with  those  of  younger  ones? 
Can  you  suggest  any  advantage  in  this  ? 1 

II.  The  head  is  subtended   by  an  involucre  of  green, 
leaf-like  bracts. 

1.  Is  there  more  than  one  row  of  bracts?     How  do  the 

outer  differ  from  the  inner  ones? 

2.  Compare  the  position  of  the  involucre  in  the  early 

morning  with  that  assumed  later  in  the  day,  and 
finally  in  the  evening;  in  clear  and  rainy  weather. 
Do  these  observations  suggest  anything  as  to  the 
function  of  the  involucre? 

III.  Taking  a  well-developed  head,  not  so  old  but  that 
a  few  of  the  flowers  of  the  center  are  still  unopened,  make 
a  longitudinal  section. 

1.  Observe  the  disk-like,  expanded  end  of  the  stalk  on 

which  the  flowers  are  borne,  the  receptacle.  Is  it 
concave  or  convex  ?  How  does  it  compare  in  this 
respect  with  the  oldest  receptacles  from  which  the 
seeds  have  fallen?  Suggest  advantages. 

2.  Note  the  order  of  development  of  the  flowers.     Cen- 

tripetal or  centrifugal  ? 

Flowers. 

These  should  be  studied  in  position  and  also  separately, 
removing  for  this  purpose  several  flowers  with  a  pair  of 
fine  forceps. 

I.  Examine  a  fully  developed  flower  throughout.  With 
a  good  lens  observe 

1  In  this  and  some  other  cases  it  will  be  necessary  to  supplement  the 
laboratory  exercises  by  out-of-door  observations. 


THE   COMPOSITE   FAMILY.  237 

1.  The  seed-like  ovary,  its   form   and   surface,  and  the 

prolongation  of  its  upper  end  into  a  short  beak, 
which  afterwards  becomes  greatly  elongated. 

2.  The  calyx,  with  its  limb  of  numerous  fine  bristles, 

pappus. 

3.  The  yellow,  ligulate  corolla. 

4.  The   stamens   inserted    on   the    corolla,    epipetalous, 

with  their  anthers  united  in  a  hollow  cylinder 
around  the  style,  syngenesious,  the  latter  soon  pro- 
jecting beyond  them  and  divided  above  into  two 
slender,  recurved,  and  finally  coiled  branches. 
(Specimens  should  be  gathered  in  the  morning 
and  also  in  the  afternoon.) 

II.  Compare  successively  older,  outer  flowers  with  the 
younger  ones,  approaching  finally  the  unopened  flowers  at 
the  center.     Note  the  different  stages  of  development  of 
the  flower,  particularly  of  the  stamens  and  pistil.    Observe 

1.  The  way  the  pollen  is  pushed  out  by  the  style. 

2.  The  short,  stiff   hairs  on  the  outer  surface   of  the 

latter. 

3.  The  papillae  on  the  inner,  stigmatic  surface  of  each 

of  its  branches.  (These  latter  require  higher 
magnification  in  order  to  be  seen  clearly.) 

III.  Imitate   the    action   of    a  bee   or   other  insect  by 
repeatedly  brushing  a  large  number  of  flowers.     Examine 
the  stigma  before  and  after  the  operation.     Is  there  any- 
thing to  favor  cross-fertilization  ? 

Fruit. 

Study  next  a  head  in  fruit.  Compare  the  hard,  seed- 
like  achenium  with  the  immature  ovary  already  examined 
and  note  differences .  What  arrangements  are  there  for 
the  dissemination  of  the  fruits  ? 


238  STUDY   OF   COMMON   PLANTS. 

Review  your  observations  and  record  them  precisely. 
I.   In  writing  an  account  of  the  flower  treat  it  first  from 
the  morphological  standpoint,  including  a  discussion  of 

1.  Original  plan  of  the  flower,  as  indicated  by  notches 

at  the  end  of  the  corolla  and  number  of  stamens. 

2.  Relation  of  calyx  and  ovary. 

3.  Other  evidences  of  modification. 

II.  Enumerate  the  various  physiological  adaptations 
such  as 

1.  Protective  arrangements. 

2.  Adaptations  for  securing  fertilization.1 

3.  Means  of  dissemination  of  seeds. 

ROBIN'S-PLANTAIN.     Erigeron  bellidifolius,  Mubl. 
Distribution. 

Where  have  you  noticed  the  plant  growing  most  abun- 
dantly ?  Does  it  appear  to  be  indigenous  or  introduced? 

General  Characters. 

Describe  the  root,  stem,  and  leaves.  Note  means  of  pro- 
tection, if  such  exist.2  It  is  said  to  produce  "  offsets." 
Verify  the  statement. 

• 

Inflorescence  and  Flowers. 

I.  Compare    the   heads    with   those    of    the  dandelion. 
What  are  the  most  striking  differences  ? 

II.  Make  a  longitudinal  section  and  examine  in  their 
natural  position,  and  also  separately,  the  purple  ray  flowers, 
and  the  small,  yellow  disk  flowers.     The   ray  flowers  are 

1  Cf.  Lubbock,  British    Wild  Flowers  in  Relation  to  Insects,  p.  Ill 
et  seq.  ;  Mtiller,  Fertilization  of  Floivers,  pp.  316-318,  350. 

2  Cf.  Kerner,  Flowers  and  their  Unbidden  Guests,  Chap.  IV. 


THE   COMPOSITE  FAMILY.  239 

ligulate,  like  those  of  the  dandelion ;  the  disk  flowers  are 
tubular. 

Do  both  ray  and  disk  flowers  have  stamens  and  pistil? 
Are  both  fertile  ? 

III.  In  older  heads  examine  the  achenia,  and  observe 
their  form  and  surface. 

IV.  How  far  do  the  arrangements  for  securing  fertiliza- 
tion correspond  with  those  observed  in  the  dandelion  ? 

V.  Compare  the  flowers  of  the  two  plants  as  regards 
modification  from  an  assumed  original  form. 

PLANTAIN-LEAVED   EVERLASTING.     Antennaria 
plantaginifolia,  Hook. 

As  in  preceding^  cases,  note  where  this  plant  occurs,  and 
record  any  peculiarities  in  its  mode  of  growth.  Notice 
particularly  its  habit  of  spreading  by  runners. 

It  will  be  observed  that  there  are  two  sorts  of  flowering 
heads,  on  different  individuals,  one,  pistillate,  more  elon- 
gated and  lighter  colored  than  the  other,  staminate,  ones. 

Study  critically  the  flowers  of  the  two  different  kinds 
of  heads.  Note  all  the  points  in  which  they  are  unlike, 
including  differences  of  pappus  and  corolla,  fertility, 
color,  size,  etc. 

Compare  the  flowers  of  this  species  with  those  of  the 
dandelion  and  robin's -plan  tain,  noting  in  each  case  points 
of  similarity  and  difference. 

RELATIONSHIP. 

A  comparative  study  should  be  made  of  as  many  other 
genera  of  Composite  as  practicable.  There  are  so  many 
species,  ranging  in  their  time  of  flowering  from  spring  to 


240  STUDY   OF   COMMON   PLANTS. 

late  autumn,  that  there  is  no  difficulty  in  obtaining  abun- 
dant material.  With  patience  and  close  attention  to 
details  of  structure,  there  is  no  reason  why  the  student 
should  not  become  thoroughly  familiar  with  the  charac- 
ters of  this  important  and  extremely  interesting  family, 
although  the  determination  of  the  limits  of  genera  and 
species  is  often  a  matter  of  great  difficulty,  owing  to  the 
number  of  intermediate  forms  and  the  tendency  to  vari- 
ability exhibited  by  many  species. 

When  as  many  species  have  been  studied  as  the  time 
will  permit,  write  a  careful  summary  of  the  morphological 
characters  in  which  they  all  agree.  This  should  be  accom- 
panied by  a  resume  of  their  physiological  peculiarities, 
especially  the  arrangements  for  securing  fertilization  and 
the  dispersal  of  seeds. 

The  Composite  constitute  the  largest  family  of  flower- 
ing plants,  including  over  one  thousand  different  genera. 
Admirably  fitted  to  survive  in  the  struggle  for  existence, 
they  have  become  distributed  throughout  the  world,  and 
retain  tenaciously  their  dominant  position.  Some  of  the 
genera  are  represented  by  so  many  species,  and  are  so 
abundant  as  to  form  in  their  season  a  characteristic  feature 
of  the  landscape,  as  is  the  case,  for  example,  with  the 
asters  and  goldenrods  in  eastern  North  America.  "  The 
numerical  preponderance,  .  .  .  and  extreme  abundance  of 
many  of  the  species,  are  due  to  the  concurrence  of  several 
characters,  most  of  which,  singly,  or  in  some  degree  com- 
bined, we  have  become  acquainted  with  in  other  families, 
but  never  in  such  happy  combinations  as  in  the  Com- 
positse."  See  Miiller's  discussion  of  these  points  in  the 
Fertilization  of  Flowers,  p.  316  et  seq. 


REVIEW    AND    SUMMARY.  241 


REVIEW    AND    SUMMARY.i 

After  such  exercises  as  those  outlined  in  the  preceding 
pages,  even  if  only  a  small  number  of  families  have  been 
studied,  the  student  can  hardly  fail  to  have  Degrees  of 
grasped  the  conception  of  degrees  of  relation-  relationship, 
ship,  a  conception  that  lies  at  the  ver}^  foundation  of  bio-* 
logical  science.2  If  we  now  extend  our  study  farther,  and 
compare  families  with  each  other,  as  we  have  been  com- 
paring their  genera,  we  shall  find  that  the  principle  is 
general,  and  that  families,  as  well  as  genera  and  species, 
show  relationships  among  themselves,  falling  naturally  into 
larger  groups  to  which  the  term  "  order  "  is  now  commonly 
applied.3  In  some  cases  these  groups  are  distinctly  marked, 
and  the  close  relationship  of  the  families  composing  them 
is  unmistakable,  while  in  others  the  affinities  of  a  family 
are  obscure.  In  an  inquiry  of  this  kind  there  are  neces- 
sarily inherent  difficulties,  and  it  must  be  said  frankly,  that, 
in  the  present  state  of  botanical  science,  it  is  impossible  to 
construct  a  system  that  will  fully  and  truthfully  represent 
the  relationship  of  families  of  plants  to  each  other.  Never- 
theless it  is  desirable  before  proceeding  farther  to  notice 

1  It  is  assumed  that  the  order  recommended  on  page  96  has  been  fol- 
lowed, or  at  least  that  the  student  has  acquired  a  reasonably  familiar 
acquaintance  with  the  prominent  families  of  flowering  plants. 

2  "  For  myself,  there   comes   from  the   eighth  year  memory  of   an 
awakening  to  the  conscious  grasp  and  knowledge  of  genus  and  species. 
I  see  it  yet  ...  in  my  lap  the  shredded  petals  of  almond,  plum,  and 
the  yellow  rose  of  Persia,  and  in  myself  sense  of  a  new  concept  and  tool 
for  classifying  and  accumulating  knowledge  through  all  life."  — TALCOTT 
WILLIAMS,  in  the  Century,  January,  1893. 

3  "Natural  order"  is  still  employed  by  many  writers  as  equivalent  to 
family,  but  the  usage  indicated  above  is  becoming  prevalent. 


242  STUDY   OF   COMMON   PLANTS^ 

some  of  the  cases  in  which  such  affinities  are  plainly  marked. 
A  few  of  these  will  serve  as  examples  of  many  others. 

The  Cruciferse,  as  we  have  seen,  are  so  plainly  defined 
by  their  cruciform,  tetradynamous  flowers,  pungent  proper- 
Groups  of  ties,  and  characteristic  fruits  and  seeds,  that  we 
families,  naturally  think  of  them  as  sharply  marked  off 
from  all  other  families  of  plants.  A  number  of  smaller 
families,  however,"  are  manifestly  related  to  them.  In  one 
of  these,  the  Capparidacese  or  caper  family,  the  flowers  are 
cruciform,  the  plants  often  pungent,  the  pods  nearly  the 
same  as  those  of  the  Cruciferae,  and  the  seeds  similar;  but 
there  are  certain  differences  of  the  embryo  and  stamens 
that  require  a  separation  of  the  two  families,  which  other- 
wise are  nearly  identical  in  their  characters.  In  like  man- 
ner the  members  of  the  Rosacese,  another  prominent  and 
well-marked  family,  show  such  plain  affinities  with  the 
Saxifragacese  that  the  differences  by  which  the  two  families 
are  distinguished  from  each  other  seem  trivial  in  compari- 
son with  their  strong  likeness.  Again,  while  the  Labiata?, 
with  their  square  stems,  opposite  leaves,  bilabiate  flowers, 
and  aromatic  properties,  form  a  most  characteristic  group 
of  plants,  their  relationship  with  the  Verbenacese,  which 
exhibit  a  number  of  characters  in  common  with  them,  is 
manifest  at  a  glance.  In  the  same  way  the  Asclepiadacese 
and  Apocynacese  show  a  remarkable  likeness,  and  this  is 
still  more  strikingly  true  of  the  Liliaceae  and  a  number  of 
families  that  form  with  them  another  marked  group,  or 
order. 

These  examples  are  sufficient  to  illustrate  the  natural 
grouping  of  families  into  orders.  Thus,  the  Labiatse  with 
Orders  and  n^De  °ther  families  constitute  the  Labiatiflorse, 
higher  groups,  the  Liliacese  with  fifteen  other  families  the 
Liliiflorse,  and  so  on.  At  present  botanists  recognize  some 


REVIEW   AND   SUMMARY.  243 

thirty  orders  of  dicotyledons,  including  about  one  hundred 
and  sixty-three  families,  and  seven  orders  of  monocotyle- 
dons with  about  forty  families,  while  the  gymnosperms 
include  three  orders  with  thirteen  families.1  The  orders 
themselves  are  associated  in  higher  groups,  which  in  their 
turn  make  up  the  great  classes  just  named.2 

Another  fact  of  prime  importance,  that  cannot  well  have 
escaped  the  student's  attention,  is  the  gradually  increasing 
complexity  of  structure,  particularly  of  the  floral  Progressive 
organs,  met  with  as  we  proceed  from  more  prim-  ^fl^f10 
itive  to  more  advanced  families.  Comparing  a  organs, 
lily,  for  example,  with  an  orchid,  or  a  buttercup  with  a 
dandelion,  it  is  plain  that  the  flowers  of  the  higher  families 
have  undergone  very  remarkable  changes  of  form  and 
structure,  although  the  fundamental  plan  may  still  be 
recognized.  These  changes  of  structure  represent,  as  a 
rule,  .progressive  adaptation  to  cross-fertilization  through 
the  agency  of  insects.  It  appears,  too,  from  all  we  can 
learn  of  them  by  comparative  study,  that  these  progressive 
modifications  have  taken  place  step  by  step  with  corres- 
ponding modifications  of  structure  and  habit  on  the  part 
of  their  visitors.  The  history  of  such  a  flower  as  that  of 
the  sweet-pea  or  violet,  of  the  milkweed  or  daisy,  must,  if 
this  view  is  correct,  reach  far  back  into  the  past,  so  far  that 
the  imagination  fails  to  reproduce  the  long  series  of  changes 
that  have  taken  place  in  the  succession  of  intervening 
generations.  A  glimpse  of  this  history,  helpful  and  satis- 

1  Cf.  Luerssen,  Botanik,  Bd.  2,  pp.  vii-x. 

2  These  groups  of  a  higher  order  are  less  satisfactorily  defined.    For  an 
attempt  at  their  systematic  presentation,  see  Goebel,  Outlines  of  Classifi- 
cation and  Special  Morphology,  pp.  xi,  xii.     The  student  will  do  well  to 
remember  that  all  such  attempts  to  represent  the  affinities  of  families  and 
higher  groups  involve  more  or  less  uncertainty,  and  that  all  classifications 
are  of  necessity  provisional. 


244  STUDY  OF 'COMMON  PLANTS. 

factory  as  far  as  it  goes,  is  given  by  Miiller  in  his  general 
retrospect  at  the  close  of  the  Fertilization  of  Floivers,  as 
follows :  "  Insects  must  operate  by  selection  in  the  same 
way  as  do  unscientific  cultivators  among  men,  who  preserve 
the  most  pleasing  or  most  useful  specimens,  and  reject  or 
neglect  the  others.  In  both  cases,  selection  in  course  of 
time  brings  those  variations  to  perfection  which  corre- 
spond to  the  taste  or  to  the  needs  of  the  selective  agent. 
Different  groups  of  insects,  according  to  their  sense  of 
taste  or  color,  the  length  of  their  tongues,  their  way  of 
movement  and  their  dexterity,  have  produced  various 
odors,  colors,  and  forms  of  flowers;  and  insects  and  flowers 
have  progressed  together  towards  perfection." 

Turning  to  the  lower  or  so-called  cryptogamic  plants,  it 
appears  that  precisely  the  same  principles  hold  good.    Ferns 
and  mosses,  quite  as  plainly  as  plants  higher  in 
A  progressive  the  scale,  exhibit  degrees  of  relationship.    Here, 
series,  ag  eisewhere,  closely  related  species  fall  natu- 

rally into  genera,  closely  related  genera  into  families,  and 
these  into  orders  and  higher  groups.  Furthermore,  a 
review  of  these  higher  groups  shows  that  the  vegetable 
kingdom  as  it  exists  to-day  presents  a  progressive  series, 
rising  from  such  simple  plants  as  Spirogyra,  and  even  more 
primitive  forms  of  the  green  algse,  through  the  liverworts 
and  mosses  to  the  vascular  cryptogams,  and  from  these  by 
an  almost  insensible  step  through  Selaginella  and  its  allies 
up  to  the  gymiiosperms  and  flowering  plants.  It  is  be- 
lieved by  those  who  have  the  most  extended  and  critical 
knowledge  of  plant  life  that  this  series  corresponds  closely 
with  the  order  of  development  of  the  vegetable  kingdom, 
and,  as  a  matter  of  fact,  it  is  found  that  the  geological 
record  strikingly  confirms  this  view.  In  earlier  geological 
times,  beginning  with  the  Silurian  Age,  marine  algse  and 


REVIEW   AND    SUMMARY.  245 

other  cellular  cryptogams  were  the  dominant  forms  of 
plant  life.  Vascular  cryptogams  appeared  in  the  Devo- 
nian ;  after  them  came  the  gymnosperms ;  then  the  mono- 
cotyledons ;  and  finally  the  different  classes  of  dicotyledons 
attained  their  present  supremacy.1 

The  life  history  of  the  flowering  plants  and  higher  cryp- 
togams still  further  confirms  the  same  view,  passing  as 
they  do  through  successive  stages  of  development  that 
repeat  in  miniature  the  history  of  past  ages  of  plant  life. 
The  fern  prothallium  in  its  earlier  stages  of  growth  is  so 
nearly  a  filamentous  green  alga  as  to  be  distinguished 
from  one  by  its  origin  rather  than  by  its  structure;  a  little 
later  it  becomes  a  flat  expansion  of  cells,  so  like  a  liver- 
wort as  to  deceive  the  inexperienced  eye ;  and  these  and 
other  phases  of  their  developmental  history  may  still  be 
recognized,  not  only  in  the  gymnosperms,  but  in  the  higher 
flowering  plants. 

From  facts  like  these,  it  seems  impossible  to  draw  any 
other  conclusion  than  that  there  has  been  from  the  earliest 
appearance  of  plant  life  on  the  elobe  a  slowly 

,     L  ,  ,  .        ,  1-1          Conclusions, 

progressive  development  irom  simpler  to  higher 
forms,  and  that  the  record  of  this  is  still  preserved  to  us 
in  the  natural  groups  that  form  the  present  vegetation  of 
the  earth. 

We  are  to  think,  then,  of  the  plants  we  have  studied 
and  those  we  have  yet  to  study,  as  in  reality  all  members  of 
one  vast  and  ancient  family,  some  closely,  others  remotely 
related,  some  still  retaining  the  simple  forms  and  habits  of 
earlier  days,  and  others,  through  a  long  course  of  selection, 
exquisitely  adapted  to  animal  structures  no  less  highly 
modified  and  adapted  to  them.  In  this  great  family,  we 

1  Lester  F.  Ward,  Am.  Nat.,  August,  1885. 


246  STUDY   OF   COMMON    PLANTS. 

have  learned  to  distinguish  species,  genera,  families,  orders, 
and  classes ;  but  these  are  simply  expressions  of  so  many 
different  degrees  of  relationship  that  pass  insensibly  into 
each  other,  and  call  for  the  exercise  of  clear  judgment, 
profound  knowledge,  and  critical  attention  to  details  on 
the  part  of  those  who  attempt  to  recognize  and  define 
them.1 

This  is  a  conception  widely  different  from  that  which 
supposes  "  that  species,  and  even  genera,  are  like  coin  from 
the  mint,  or  bank-notes  from  the  printing  press,  each  with 
its  fixed  marks  and  signature,  which  he  that  runs  may 
read,  or  the  practiced  eye  infallibly  determine,"  but  "there 
is  grandeur  in  this  view  of  life,  with  its  several  powers, 
having  been  originally  breathed  by  the  Creator  into  a  few 
forms  or  into  one ;  and  that,  whilst  this  planet  has  gone 
cycling  on  according  to  the  fixed  law  of  gravity,  from  so 
simple  a  beginning,  endless  forms  most  beautiful  and  most 
wonderful,  have  been  and  are  being  evolved."2 

^  After  some  months  of  such  training  as  is  outlined  in  the  preceding 
exercises,  the  student  should  be  prepared  to  take  up  with  profit  a  study 
of  the  flora  of  the  region  in  which  he  lives.  In  this  way,  with  an  indefi- 
nite amount  of  painstaking,  independent,  and  long-continued  work,  he 
will  gradually  become  more  familiar  with  the  systematic  grouping  of 
plants  and  accumulate  for  himself  the  evidence  that  more  and  more  con- 
firms the  conclusion  formulated  above. 
2  Darwin,  Origin  of  Species,  p.  429. 


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